A Complete Guide to Towing Terminology: Subchapter M

Let’s not sugarcoat it—if you’re managing towing vessels subject to Subchapter M, the paperwork alone can feel like a full-time job. Between coast guard inspections, internal audits, training requirements, and keeping up with your safety management system TSMS, it’s easy to lose track of what half the terms even mean.

But here’s the bottom line: if your vessels operate on U.S. waters—even if you only perform occasional towing—you’re expected to speak the same language as the United States Coast Guard. That language now comes straight from the standardized glossary included in Subchapter M regulations.

Why? Because for years, regional slang and informal phrases made it tough for inspected vessels to demonstrate compliance—especially when annual coast guard inspections came around. And when it comes to safety, terminology isn’t just semantics. It’s risk mitigation.

Key Takeaways

• Subchapter M is law—there’s no “opt-out” if your vessels operate in the U.S. or on salt water routes.
• You must have a valid certificate of inspection and prove vessel compliance through either TSMS or direct coast guard inspection.
• Language counts. The standardized towing terminology published by the Coast Guard removes ambiguity and helps prevent issues during inspections.
• Even if you only perform occasional towing, you may still be considered an inspected vessel.
• You’re responsible for maintenance, construction, training, and overall safety operations—regardless of whether you’re self-managed or working with third party organizations.
• The American Waterways Operators helped shape many of these provisions over a six year period of industry input.

Subchapter M Glossary: The Terms You’re Expected to Know

Able Seafarer-Deck: a rating qualified in accordance with the provisions of Regulation IV5 of the STCW Convention.

Able Seafarer-Engine: a rating qualified in accordance with the provisions of Regulation III/5 of the STCW Convention.

Abrasion Resistance: material’s ability to resist exterior damage due to frictional contact.

Acceptable Identification:

1. Passport;
2. U.S. Permanent Resident Card;
3. U.S. Merchant Mariner Document;
4. U.S. Merchant Mariner Credential;
5. Transportation Worker Identification Credential (TWIC) issued by the Transportation Security Administration under 49 CFR part 1572; or
6. Seafarer’s Identification Document (SID) issued by or under the authority of the government of a country that has ratified the International Labour Organization Seafarers’ Identity Documents Convention (Revised), 2003 (ILO 185), meeting all the requirements ofILO 185.

Accommodation: a cabin, or other covered or enclosed place, intended to be occupied by persons. Each place in which passengers and special personnel is carried is considered an accommodation, whether or not it is covered or enclosed. Accommodations include, but are not limited to, halls, dining rooms, mess rooms, lounges, corridors, lavatories, cabins, offices, hospitals, cinemas, game and hobby rooms, and other similar places open to persons on board.

Accommodation Space: any public space such as a hall, dining room, mess room, lounge, corridor, lavatory, cabin, office, hospital, cinema, game and hobby room, pantry that contains no cooking appliances, and a similar space open to passengers and crew.

Act of God: an act occasioned by an unanticipated grave natural disaster.

Acts of Piracy: acts of armed robbery against ships and any other security incidents directed against a ship, where the term “ship” is understood to include all persons on board.

Advance: distance gained in the direction of the original course when turning a ship, measured from the point at which the rudder is put over to the point where the ship has changed heading 90 degrees.

After Deck: aft of amidships portion of a vessel.

Agent: means any person, partnership, firm, company or corporation engaged by the owner or charterer of a vessel to act in their behalf in matters concerning the vessel.

Air Draft: The distance from the surface of the water of the highest point on a vessel.

Amidships: In or toward the middle of a ship.

Anchor Shackle: AU-shaped fitting with pin.

Anchor Windlass: The machine used to hoist and lower anchors.

Anniversary Date: The day and the month of each year, which corresponds to the date of expiration of the Certificate of Inspection.

Anti-Exposure Suit: A protective suit designed for use by rescue boat crews and marine evacuation system parties.

Apprentice Mate (Steersman) of Towing Vessels: A credentialed mariner in training to perform bridge watchkeeping duties onboard a towing vessel, who must be under the direct supervision and in the continuous presence of a master or mate (pilot) of towing vessels.

Approved Lifesaving Appliance: Carrying an approval granted by the Commandant under subchapter Q of 46 CFR §10.107 subchapter B.

Approved Training: Training that is approved by the Coast Guard or meets the requirements of§ 10.408 of 46 CFR §10.107 subchapter B.

Area Committee: An Area Committee established under subsection (j) of 33 u.s.c. §1321.

Area Contingency Plan: An Area Contingency Plan prepared under subsection U) of 33 u.s.c. §1321.

Articulated Tug Barge or ATB: Any tug-barge combination, which, through the use of an articulated or “hinged” connection system between the tug and barge, allows independent movement in the critical area of fore and aft pitches.

Assessment: Evaluation

Assistance Towing: Towing a disabled vessel for consideration.

 Assistant Engineer: A qualified officer in the engine department.

Assistant Engineer for National Endorsements: A qualified officer in the engine department other than the chief engineer.

Associated Ship Unit: A portable VHF transmitter for use in the vicinity of the ship station with which it is associated.

Assumed Average Weight Per Person: The weight calculated in accordance with 46 CFR §170.090 of this part.

Athwartship: At right angles to the fore and aft centerline of a ship or boat.

Attachment Point: Point of attachment between the tow and the towed vessel. The attachment point transmits the towing load from the towline to the vessel.

Authorized Official: Includes, but is not limited to, a Federal, State or local law enforcement officer.

Automatic Identification System (AIS): A maritime navigation safety communications system standardized by the International Telecommunication Union (ITU) and adopted by the International Maritime Organization (IMO) that provides vessel information, including the vessel’s identity, type, position, course, speed, navigational status and other safety-related information automatically to appropriately equipped shore stations, other ships, and aircraft; receives automatically such information from similarly fitted ships; monitors and tracks ships; and exchanges data with shore-based facilities.

Automatic Towing Machine: A device, which maintains safe tension on the hawser during towing without action by the operator.

Auxiliary Sailing Vessel: A vessel capable of being propelled both by mechanical means and by sails.

Auxiliary Towline: A tug’s spare or secondary hawser used for multiple tows or secondary functions such as an emergency towline.

Backing down: Using astern throttle to rapidly reduce the forward speed of a tug. 

Bail: The part of a pelican hooks or chain stopper that holds the hook closed.

Ballast: The weight added to a ship or boat to ensure stability; primarily water.

Ballast Control Operator or BCO: An officer restricted to service on mobile offshore drilling units (MODUs) whose duties involve the operation of the complex ballast system found on many MODUs. When assigned to a MODU, a ballast control operator is equivalent to a mate on a conventional vessel.

Ballast Tank: Any tank or hold on a vessel used for carrying ballast water, whether or not the tank or hold is designed for that purpose.

Ballast Water: Any water and suspended matter taken on board a vessel to control or maintain: trim, draft, stability, or stress of the vessel, regardless of how it is carried.

Barge: Means a non-self propelled vessel as defined in 46 U.S.C 102.

Barge Supervisor or BS: An officer restricted to service on MODUs whose duties involve support to the offshore installation manager (OIM) in marine-related matters including, but not limited to, maintaining watertight integrity, inspecting and maintaining mooring and towing components, and maintaining emergency and other marine-related equipment. A barge supervisor, when assigned to a MODU, is equivalent to a mate on a conventional vessel.

Barrel: Means 42 United States gallons at 60 degrees Fahrenheit.

Beach Gear: A generic term for specialized ground tackle, purchases, and ancillary equipment used to extract a grounded ship.

Beam or B: The maximum width of a vessel from:

1. Outside of planking to outside of planking on wooden vessels
2. Outside of frame to the outside of the frame of all other vessels. 

Beam Sea: A sea that runs athwart the vessel’s course.

Beam Wind: A wind that blows athwart the vessel’s course.

Bear Down: To approach the target.

Beaufort No.: A numerical value (from Oto 12) used for rating wind velocity, in ascending strength.

Bight: A loop in a line.

Bilge: Lowest extremity of the engine room.

Billboard: An inclined platform used to stow an anchor for rapid deployment.

Bird  Caging, Bird Nesting, or Backlashing: The phenomenon of wires flaring out around the full diameter of a wire rope, with resulting kinks in the wires. This can occur when there is a sudden release of a heavy load on a wire rope.

Bitter End: The absolute end of a length of line or cable, especially the last link of anchor chain in the chain locker.

Bitts: Metal posts aboard vessels supported in the frames or other substantial structural members below decks to which mooring or towing lines are made fast and may have either horns or cavals.

Boat Deck: Deck where survival crafts are located; traditionally the 01 deck.

Boatswain: Means the leading seaman and immediate supervisor of deck crew who supervises the maintenance of deck gear.

Bollard: Single posts secured to a wharf or pier and used for mooring vessels by means of lines extending from the vessel.

Bollard Pull: The maximum pulling power that a tug can generate under a static pull.

Boundary Line: Marks the dividing point between internal and offshore waters for the purposes of several U.S. statutes and, with exceptions, generally follows the trend of the seaward, high-water shorelines. See 46 CFR part 7.

Bow: Forward most part of the vessel.

Bow (of the) Shackle: The curved end of a shackle.

Bow Thruster: A propulsor at the bow of the ship, which aids in moving the bow sideways.

Bow Winch: A basic bow winch that stores, pays out, and heaves in bow lines.

Bowline: A classic knot that forms a loop that will not slip or become tighter under tension.

Breaking Out: When an inland towboat turns loose from a tow to reconnect or be relieved of the tow.

Breaking Strength: The actual or ultimate rated load required to pull a wire, strand, or rope to destruction.

Breaking Tow: 

1. The process carried out by a tug towing on a hawser to disconnect from the tow.
2. The process carried out by an inland towboat to take barges out of the tow to drop them at a fleet or dock or when locking, or to break the tow at a predetermined point utilizing another towing vessel. 
3. For coastwise notch and ATB tugs, the process of disconnecting push gear or retracting / releasing connection devices (getting out of the notch).

Breakwater: Structure that shelters a port or anchorage from the sea.

Breasted Tug: One or more tugs towing a unit astern with independent tow wires.

Breasted Tow: One or more units towed alongside the other.

Bridge-to-Bridge Station: A radio station located on a ship’s navigational bridge or main

control station operating on a specified frequency which is used only for navigational communications, in the 156-162 MHz band.

Bridles: A length of chain or wire extending from the bow of a tow. Usually refers to the rigging of a tow with two legs from the tow’s bow to a flounder plate.

Broach: To be turned broadside to a surf or heavy sea.

Bulbous Bows: An extension of the bow of a ship below the water line that is designed to reduce wave drag.

Bulk: Material in any quantity that is shipped, stored, or handled without the benefit of package, label, mark or count and carried in integral or fixed independent tanks.

Bulkhead: Walls or partitions within a ship, generally referring to those with structural functions such as strength or water-tightness.

Bulkhead Deck: The uppermost deck to which watertight bulkheads and the watertight sbel1 extend.

Bull Rope: Colloquial term referring to a towing hawser.

Bullnose: Closed chock at the bow of a ship or end of a Lock Wall.

Bulwark: Section of a ship’s side continued above the main deck as protection against heavy weather.

Button: A heavy steel casting found on lock walls or as deck fittings on a vessel that looks like a short mushroom-shape bitt.

Cable: A heavy wire of great strength. Applications include attachment to anchors and towing. Also a unit of length, equivalent to approximately 100 fathoms or 600 feet.

Calculated Risk: Accepting an operation or decision based on less than satisfactory conditions. As applied to towing, accepting a tow when the tow’s material condition, seaworthiness, weather, etc.makes the tow less than satisfactory. This should be rarely used as a basis of acceptance of the tow.

Calm Water Resistance: The hydrodynamic resistance created by a tow without the

influence of waves created by the weather, tug, tow, or other outside influences; approximates steady tension.

Camber: The convexity of a vessels deck beam to direct water to the freeing ports.

Caprail: Rounded radius on the stem of a towing vessel, over that the sweep of the tow wires rides.

Capstan: A rotating device with a vertical axis used for controlled deployment and retrieval of lines.

Captain of the Port: The Coast Guard officer designated by the Commandant to command a Captain of the Port Zone as described in part 3 of 33 CFR §160.3.

Careen: To cause a vessel to have a permanent list to one side. Specifically, as in a dry dock, to rotate the deck placing one sidewall below the water line. This is done to reduce the beam to allow passage through canals or other restricted waterways.

Cargo: Any goods or merchandise shipped in domestic or international trade, excluding provisions and stores aboard the carrying vessel

Cargo Area: The part of a vessel that includes the cargo tanks and other tanks into which cargo or cargo vapors are intentionally introduced, holds containing these tanks, an intervening space within, between, below, or outboard of these tanks or holds, and the deck area over the length and beam of the vessel above these tanks, holds, or spaces.

Cargo Control Station: A location that is manned during cargo transfer operations for the purpose of directing or controlling the loading or unloading of cargo.

Cargo Engineer: A person holding an officer endorsement on a dangerous­ liquid tankship or a liquefied-gas tankship whose primary responsibility is maintaining the cargo system and cargo-handling equipment.

Cargo Handling Room: Any enclosed space where cargo is pumped, compressed, or processed. Examples of cargo handling rooms are pump rooms, compressor rooms, and cargo valve rooms.

Cargo Ship Safety Radio Certificate: A certificate issued after a ship passes an inspection of the required radiotelegraph, radiotelephone or GMDSS radio installation. Issuance of this certificate indicates that the vessel complies with the Communications Act and the Safety Convention.

Cargo Ship Safety Radiotelegraphy Certificate: A certificate issued after a ship passes an inspection of a radiotelegraph installation. Issuance of this certificate indicates that the vessel complies with the Communications Act and the Safety Convention.

Cargo Vessel: Means any vessel that is not a passenger vessel carrying cargo.

Carpenter Stopper: A mechanical device consisting of a cover that encloses a sliding wedge within the body that can be opened by knocking away a latch that holds them closed. Used for stopping off wire rope.

Carried in Bulk: A commodity that is loaded or carried on board a vessel without containers or labels and received and handled without mark or count.

Carrying Freight for Hire: The carriage of any goods, wares, or merchandise, or any other freight for a consideration, whether directly or indirectly flowing to the owner, charterer, operator, agent, or any other person interested in the vessel.

Category A Machinery: Any any space and trunks and ducts to such a space that Space contains:

1. Internal combustion machinery used for main propulsion;
2. Internal combustion machinery used for purposes other than main propulsion where the total aggregate power is at least 500 brake horsepower;
3. Internal combustion machinery that uses a fuel that has a flash point less than 43.3°C (l 10°F); or
4. One or more oil fired boilers or oil fuel units.

Catenary: The downward curve or sag of a rope, wire, or chain suspended between two points

Caval: Substantial horizontal structure on an H-Bitt for use of securing lines.

Center of Gravity (CG): The point in a ship where the sum of all forces and moments of weight is zero.

Ceremonial License: A document that reflects a mariner’s existing national officer endorsement and is suitable for framing, but is not valid for use as a Merchant Mariner Credential (MMC).

Certain Dangerous Cargos (CDC): Includes any of the following:

1. Division 1.1 or 1.2 explosives as defined in 49 CPR 173.50.
2. Division 1.5D blasting agents for which a permit is required under 49 CPR 176.415 or, for which a permit is required as a condition of a Research and Special Programs Administration exemption.
3. Division 2.3 “poisonous gas”, as listed in 49 CPR 172.101 that is also a “materia1 poisonous by inhalation” as defined in 49 CPR 171.8, and that is in a quantity in excess of 1 metric ton per vessel.
4. Division 5.1 oxidizing materials for which a permit is required under 49 CPR 176.4 I 5 or for which a permit is required as a condition of a Research and Special Programs Administration exemption.
5. A liquid material that has a primary or subsidiary classification of Division 6.1 “poisonous material” as listed in 49 CFR 172.101 that is also a “material poisonous by inhalation,” as defined in 49 CFR 171.8 and that is in a bulk packaging, or that is in a quantity in excess of 20 metric tons per vessel when not in a bulk packaging.
6. 6) Class 7, “highway route controlled quantity” radioactive material or “fissile material, controlled shipment,” as defined in 49 CFR 173.403.(7) All bulk liquefied gas cargo carried under 46 CFR 151.50-31 or listed in 46 CFR 154.7 that is flammable and/or toxic and that is not carried as certain dangerous cargo Residue (CDC Residue)

Certain Dangerous Cargo Residue (CDC Residue): Includes any of the following:

1. (I) Ammonium nitrate in bulk or ammonium nitrate based fertilizer in bulk remaining after all saleable cargo is discharged, not exceeding 1,000 pounds in total and not individually accumulated in quantities exceeding two cubic feet.
2. For bulk liquids and liquefied gases, the cargo that remains onboard in a cargo system after discharge that is not accessible through normal transfer procedures, with the exception of the following bulk liquefied gas cargoes carried under 46 CFR
   1. §151.50-31 or listed in 46 CFR §154.7:
   2. b.Ammonia, anhydrous;
   3. Chlorine;
   4. Ethane;
   5. Ethylene oxide;
   6. Methane (LNG);
   7. Methyl bromide;
   8. Sulfur dioxide; and
   9. Vinyl chloride.

Certificated: When applied to tank vessels refers to a vessel covered by a certificate of inspection issued by the Coast Guard; when applied to men employed on tank vessels, the term refers to a certificate of ability issued by the Coast Guard.

Certificated Person: A person holding a U.S. Merchant Mariner’s Document or Merchant Mariner Credential with an endorsement as a lifeboatman or another inclusive rating under part 12 of 46 CFR §199.30.

Chafing Gear: Material used to prevent chafing and wear on both the hawser and the tug’s structure.

Chafing Pendant: A length of chain used to reduce chafing or wearing.

Chain Bridle: Two legs of chain joined by a flounder’s plate extending from the bow of a unit towed.

Chain Connecting Link: See “Detachable link.”

Chain Pendant: A single length of chain extending from the bow of a tug used as a towing connection element, usually fitted with an eye at one or both ends.

Chain Shackle: AU-shaped fitting with a pin used for chain connections in a towing rig.

Chain Stopper: A device used to secure chain, thereby relieving the strain on the windlass; also used to secure the anchor in the housed position in the hawsepipe.

Charterer: The person or organization that contract for the majority of the carrying capacity of a ship for the transportation of cargo to a stated port for a specified period. This includes “time charterers” and “voyage charterers.”

Chemical Tanker: A tank vessel that is certificated to carry or carries chemicals in bulk as cargo or cargo residue. For the purposes of qualifying for an STCW endorsement for advanced chemical tanker cargo operations, this includes tank barges.

Chicken Coop: Enclosed steering station above the wheelhouse with restricted size and bridge controls.

Chief Engineer: The senior engineer responsible for the mechanical propulsion and the operation and maintenance of the mechanical and electrical installations of the vessel.

Chief Mate: The deck officer next in rank to the master and upon whom the command of the vessel will fall in the event of incapacity of the master.

Child: For the purpose of determining the number of lifejackets required under 46 CFR §199.30, means a person less than 41 kilograms (90 pounds) in mass.

Chinese Moor: Denotes that two ships are alongside each other in such a manner that the stem of one is facing the same direction as the bow of the other.

Chock: A heavy smooth-surfaced fitting usualJy located near the edge of the weather deck through which wire ropes or fiber hawsers may be led.

Christmas Tree Tow: Not used commercially. This type of arrangement as defined/illustrated (2002 edition of the US Navy Towing Manual Pg I-7 and 1-14) utilizes underriders and various jewelry; may be used in commercial towing for towing more than two vessels on one tow wire and genera11y would be made up in an anchorage area with assist tugs. The method shown in the Navy manual on page 1-14 involved extra rigging and line handling for towing the barges off the dock. Double drum tandem towing bas replaced the need for Christmas Tree rigging.

Civilian Nautical School: Any school or branch thereof operated and conducted in the United States, except State nautical schools and schools operated by the United States or any agency thereof, which offers instruction for the primary purpose of training for service in the Merchant Marine.

Classification Requirements: Applicable rules and supplementary requirements of recognized classification society.

Cleat: An anvil-shaped deck fitting for securing or belaying lines (referred to as a Kevel on Western Rivers).

Cleat Guard: A device secured to the ends of the cleat to prevent line fouling. 

Clip, Wire: Fitting for clamping two parts of wire rope to each other.

Closed Spelter Socket: A wire rope termination.

Coaming: Vertical plating built around a hatchway to prevent downward flooding.

Coast Guard: The organization established and continued under section 1 of title 14.

Coast Guard District Commander: An officer of the Coast Guard designated as such by the Commandant to command all Coast Guard activities within his or her district, which includes the inspection, enforcement, and administration of Subtitle II, Title 46 U.S. Code; Title 33 U.S. Code; and regulations issued under these statutes.

Coast Guard District  Response Group: A Coast Guard District Response Group established under Response Group subsection G) of 46 CFR §24.10-1.

Coast Guard-Accepted:

1. That the Coast Guard has officially acknowledged in writing that the material or process at issue meets the applicable requirements;
2. That the Coast Guard has issued an official policy statement listing or describing the material or process as meeting the applicable requirements; or
3. That an entity acting on behalf of the Coast Guard under a Memorandum of Agreement has determined that the material or process meets the applicable requirements.

Coast Guard-Accepted QSS Organization: An entity that has been approved by the Coast Guard to accept and monitor training on behalf of the Coast Guard.

Coastwise: Under this designation shall be included all tank vessels normally navigating the waters of any ocean or the Gulf of Mexico 20 nautical miles or less offshore.

Coastwise Seagoing Vessel:  A vessel that is authorized by its Certificate of inspection

to proceed beyond the Boundary Line established in part 7 of 46 CFR §10.107 subchapter B.

Coastwise Voyage: Is a domestic voyage and means a voyage in which a vessel proceeds:

1. From one port or place in the United States to another port or place in the United States 
2. From a port or place in a United States possession to another port or place in the same possession, and passes outside the line dividing inland waters from the high seas; or
3. From a port or place in the United States or its possessions and passes outside the line dividing inland waters from the high seas and navigates on the high seas, and then returns to the same port or place.

Cofferdam: A void or empty space separating two or more compartments for the purpose of isolation or to prevent the contents of one compartment from entering another in the event of the failure of the walls of one to retain their tightness.

COLREG: U.S. Coast Guard Rules of the Road.

Combination Carrier: A tank vessel designed to carry alternatively liquid and solid cargoes in bulk.

Combustible Liquid: Any liquid having a flashpoint above 80 °F (as determined from an open-cup tester, as used for test of burning oils). In the regulations of 46 CFR §30.10-15, combustible liquids are referred to by grades, as follows:

1. Grade D. Any combustible liquid having a flashpoint below 150 °F. and above 80 °F.
2. Grade E. Any combustible liquid having a flashpoint of 150°F. or above.

Commandant: The Commandant of the Coast Guard or an authorized representative of the Commandant.

Commanding Officer Marine Safety Center (CO, MSC) : A district commander described in 33 CPR part 3 whose command includes a merchant marine technical office or an authorized representative of the district commander.

Commercial Communications:  Communications between coast stations and ship stations aboard commercial transport vessels, or between ship stations aboard commercial transport vessels, which relate directly to the purposes for which the ship is used including the piloting of vessels, movements of vessels, obtaining vessel supplies, and scheduling of repairs.

Commercial Service: Includes any type of trade or business involving the transportation of goods or individuals, except service performed by a combatant vessel.

Communicable Disease: Any disease capable of being transmitted from one person to another directly, by contact with excreta or other discharges from the body; or indirectly, via substances or inanimate objects contaminated with excreta or other discharges from an infected person. Pursuant to 42 U.S.C. 12113, the Department of Health and Human Services periodically publishes in the Federal Register a list of infectious and communicable diseases that are transmissible through the food supply, and that list provides examples of communicable diseases for purposes of§ 10.304 of this title. 

Communications Service: An entity responsible for all or part of the delivery of security Provider (CSP) alert messages from ships to competent authorities.

Company Security Officer (CSO): A company official from the vessel’s owner and/or operator who will be responsible for developing, maintaining, and enforcing the Company security plans asset out in this document.

Compartment: Room or space on board ship.

Competent Authority: Designated authority that receives SSAS alerts from ships and informs the administration of the appropriate flag State.

Competent Person: As used in part 13 only, Means a person designated as such under 29 CFR 1915.7.

Compressed Natural Gas: Natural gas (predominantly methane, CH4) that has been (CNG) compressed to a pressure typically in the range of 2900-3600 psi (200-248 bar) for ease of storage or transport.

Consideration: An economic benefit, inducement, right, or profit including pecuniary payment accruing to an individual, person, or entity, but not including a voluntary sharing of the actual expenses of the voyage, by monetary contribution or donation of fuel, food, beverage, or other supplies.

Constructed: 

1. The vessel’s keel was laid; or
2. Construction identifiable with the vessel began and assembly of that vessel commenced comprising of 50 metric tons or at least I percent of the estimated mass of all structural material, whichever is less.

Constructional Stretch: The elongation of a wire rope caused by a virgin rope’s helical strands constricting the core during initial loading. This property is no longer exhibited after several loadings.

Contiguous Zone: The entire zone established or to be established by the United States under article 24 of the Convention on the Territorial Sea and the Contiguous Zone.

Control Space: An enclosed space in which is located a ship’s radio, main navigating equipment, or emergency source of power or in which is located centralized fire recording or fire control equipment, but not including firefighting apparatus that must be located in the cargo area or individual pieces of firefighting equipment.

Controllable Pitch Propeller (CPP): A screw propeller with separately mounted blades and in which the pitch of the blades can be changed, and even reversed, while the propeller is in operation.

Convention Measurement System: A U.S. tonnage measurement system that is based on and complies with the requirements of the International Convention on Tonnage Measurement of Ships, 1969. Gross tonnages assigned under this system are referred to in terms of gross tonnage, ITC (GT ITC) or gross tonnage (GT). This system uses total molded volume as its basis. This system is not available for measurement of vessels with an overall length less than 24 meters (79 feet). Requirements for measurement under this system and are detailed in 46 CFR 69, subpart B. m are detailed in 46 CFR 69, subpart B.  are detailed in 46 CFR 69, subpart B.Conviction: Means that the applicant for a Merchant Mariner Credential has been found guilty, by judgment or plea by a court of record of the United States, the District of Columbia, any State, territory, or possession of the United States, a foreign country, or any military court, of a criminal felony or misdemeanor or of an offense described in section 205 of the National Driver Register Act of 1982, as amended (49 U.S.C. 30304). If an applicant pleads guilty or no contest, is granted deferred adjudication, or is required by the court to attend classes, make contributions of time or money, receive treatment, submit to any manner of probation or supervision, or forgo appeal of a trial court’s conviction, then the Coast Guard will consider the applicant to have received a conviction. A later expungement of the conviction will not negate a conviction unless the Coast Guard is satisfied that the expungement is based upon a showing that the court’s earlier conviction was in error.

Cooperative Vessel Traffic  Services (CVTS): The system of vessel traffic management established and jointly operated by the United States and Canada within adjoining

waters. In addition, CVTS facilitates traffic movement and anchorages, avoids jurisdictional disputes, and renders assistance in emergencies in adjoining United States and Canadian waters.

Core: The axial member of a wire rope, about which the strands are laid. It may consist of wire strand, wire rope, synthetic or natural fiber, or solid plastic.

Cotter Keys: Also called cotter pins, are used to secure or block nuts, clevises, etc. Driven into holes in the shaft, the eye prevents complete passage, and the split ends, deformed after insertion, prevent withdrawal.

Coupler Room: Area housing coupling equipment (Artubar, Interconn, JAK, etc.)

Credential: Means any or all of the following:

1. Merchant mariner’s document.
2. License.
3. STCW endorsement.
4. Certificate of registry.
5. Merchant Mariner Credential. 

Crest: The top of a wave.

Crew: All persons carried on board the vessel to provide navigation and maintenance of the vessel, its machinery, systems, and arrangements essential for propulsion and safe navigation or to provide services for other persons on board.

Crew Endurance Management System: A system of proven practices for managing endurance risk factors that affect operational safety and crewmember efficiency in the (CEMS) maritime industry.

Crewmember: All persons carried on board the vessel to provide navigation and maintenance of the vessel, its machinery, systems, and arrangements essential for propulsion and safe navigation or to provide services for other persons on board.

Criminal Record Review: The process or action taken by the Coast Guard to determine whether an applicant for, or holder of, a credential is a safe and suitable person to be issued such a credential or to be employed on a vessel under the authority of such a credential.

Crude Oil: A liquid hydrocarbon mixture occurring naturally in the earth whether or not treated to render it suitable for transportation, and includes crude oil from which certain distillate fractions may have been removed, and crude oil to which certain distillate fractions may have been added.

Crude Oil Tanker: A tanker engaged in the trade of carrying crude oil. 

Current Edition: The most recent published version of a publication, chart, or map required by 46 CFR §164.72.

Currently Corrected Edition: A current or previous edition of a publication required by 46 CFR §164.72, corrected with changes that come from Notices to Mariners (NTMs) or Notices to Navigation reasonably available and that apply to the vessel’s transit. Hand-annotated river maps from the U.S. Army Corps of Engineers (ACOE) are currently corrected editions if issued within the previous 5 years.

Cutwater: The stem of a ship, the forward most portion of the bow, which cuts the water as the ship moves.

Dangerous Drug: A narcotic drug, a controlled substance, or a controlled­ substance analogue (as defined in section 102 of the Comprehensive Drug Abuse and Control Act of 1970 (21 U.S.C. 802)).

Dangerous liquid or DL: A liquid listed in 46 CFR 153.40 of this chapter that is not a liquefied gas as defined in this part. Liquid cargoes in bulk listed in 46 CFR part 153, Table 2, of this chapter are not dangerous-liquid cargoes when carried by non-oceangoing barges.

Day : Means:

1. For the purpose of complying with the service requirements of 46 CFR §10.107 subchapter B, 8 hours of watchstanding or day­ working not to include overtime. On vessels authorized by 46 U.S.C. 8104 and 46 CFR 15.705, to operate a two-watch system, a 12-hour working day may be creditable as 1 1/2 days of service. On vessels of less than 100 ORT, a day is considered as 8 hours unless the Coast Guard determines that the vessel’s operating schedule makes this criteria inappropriate; in no case will this period be less than 4 hours. When computing service on MODUs for any endorsement, a day ofMODU service must be a minimum of 4 hours, and no additional credit is received for periods served over 8 hours. For cadet service on a training ship furnished by the Maritime Administration under 46 CFR §310.4, a day may be creditable as I1’2 days of service.
2. Where the word day is applied to the use of a specific frequency assignment or to a specific authorized transmitter power, its use means transmission on the frequency assignment or with the authorized transmitter power during that period of time included between one hour after local sunrise and one hour before local sunset.
3. Where the word day occurs in reference to watch requirements, or to equipment testing, its use means the calendar day, from midnight to midnight, local time.

Deadweight or DWT: The difference in metric tons between the lightweight displacement and the total displacement of a vessel measured in water of specific gravity 1.025 at the load waterline corresponding to the summer freeboard assigned according to 46 CFR, subchapter E.

Deck: Nautical name for floors and are numbered from the main deck

00 up.

Deck Crew (excluding  individuals serving under their officer endorsement): Means, as used in 46 U.S.C. 8702, only the following members of the deck department: able seamen, boatswains, and ordinary seamen.

Deck Department: The department aboard a ship responsible for navigation, cargo, command, and control functions.

Declaration of Security: An agreement to be executed between the responsible vessel and (DOS) waterfront facility and provides a means for ensuring that the critical security concerns are properly addressed and security will remain in place throughout the vessel’s activities within the port. Security for the vessel is properly addressed by delineating the responsibilities for security arrangements and procedures between a vessel and waterfront facility.

Deshackling Kit: A tool set used to assemble and disassemble detachable links. Tools included in these sets are hammers, punches, lead pellets, spare taper pins, and hairpins.

Designated Areas: Those areas within pilotage waters for which first-class pilot’s endorsements are issued under part 11, subpart G, of 46 CFR §10.107 subchapter B, by the Officer in Charge, Marine Inspection (OCMI). The areas for which first-class pilot’s endorsements are issued within a particular Marine Inspection Zone and the specific requirements to obtain them may be obtained from the OCMI concerned.

Designated Duty Engineer or DDE: A qualified engineer, who may be the sole engineer on vessels with a periodically unmanned engine room.

Designated Examiner or DE: A person who has been trained or instructed in techniques DE of training or assessment on towing vessels and is otherwise qualified to evaluate whether an applicant has achieved the level of proficiency required to hold a towing vessel endorsement on a merchant mariner credential (MMC). The Coast Guard must approve this person.

Designated Medical Examiner: A licensed physician, licensed physician’s assistant, or licensed nurse practitioner who has been trained and approved to conduct medical and physical examinations of merchant mariners on behalf of the U.S. Coast Guard and may be delegated limited authority to grant waivers and approve physical medical suitability for service.

Detachable Link: A joining link that can be opened and is used to connect chain to mooring, towing, or beach gear equipment

Detection: The determination of the location of survivors or survival craft.

Deterioration: Single defect in steel vessels (age, inadequate maintenance, working of the hull structure, chemical or erosive action of the cargoes carried, electrolysis, local wear, some improper feature of design, etc.).

Deviation: Any departure from any rule in 33 CFR §160.3. 

Dewatering: Process used to remove  flood water from a ship.

Die Lock chain: Chain formed by forging.

Digital Selective Calling: A synchronous system developed by the International (DSC) Telecommunication Union Radio communication (ITU-R) Sector, used to establish contact with a station or group of stations automatically by means of radio. The operational and technical characteristics of this system are contained in ITU-R M.493-13 and ITU-R M.541-9 (both incorporated by reference, see §80.7 and see subpart W of 47 CFR §80.5).

Dipped Shackle, Padeye: The placement of a shackle through a padeye or connection, as opposed to passing the pin of the shackle through opening in the padeye. The padeye is shaped to accept a shackle as described.

Direction Finder (Radio Compass): Apparatus capable of receiving radio signals and taking bearings on these signals from which the true bearing and direction of the point of origin may be determined.

Directly Supervised/Direct Supervision (only when referring to issues related to tankermen : Being in the direct line of sight of the person-in-charge or when maintaining direct, two-way communications by a convenient, referring to issues related reliable means, such as a predetermined working frequency over a handheld radio.

Director, Vessel Traffic Services: The Coast Guard officer designated by the Commandant to command a Vessel Traffic Service (VTS) as described in part 161 of this chapter.

Disabled Vessel: A vessel that needs assistance, whether docked, moored, anchored, aground, adrift or underway. This does not mean a barge or any other vessel not regularly operated under its own power.

Discharge: Includes, but is not limited to, any spilling, leaking, pumping, pouring, emitting, emptying or dumping, but excludes:

1. Discharges in compliance with a permit under section §1342 of 33 U.S.C.,
2. Discharges resulting from circumstances identified and reviewed and made a part of the public record with respect to a permit issued or modified under section 1342 of 33 U.S.C., and subject to a condition in such permit, 1
3. Continuous or anticipated intermittent discharges from a point source, identified in a permit or permit application under section §1342 of 33 U.S.C., which are caused by events occurring within the scope of relevant operating or treatment systems, and
4. Discharges incidental to mechanical removal authorized by the President under subsection (c) of this section.

Discharge Head: A measurement of the discharge pressure of a pump in feet of water, which takes into account friction losses and velocity head.

Displacement: The weight of water displaced by a vessel.

Distress Signal: The distress signal is a digital selective call using an internationally recognized distress call format in the bands used for terrestrial communication or an internationally recognized distress message format, in which case it is relayed through space stations, which indicates that a person, ship, aircraft, or other vehicle is threatened by grave and imminent danger and requests immediate assistance.

1. In radiotelephony, the international distress signal consists of the enunciation of the word “Mayday”, pronounced as the French expression “m’aider”. In case of distress, transmission of this particular signal is intended to ensure recognition of a radiotelephone distress call by stations of any nationality.
2. For GMDSS, distress alerts result in an audible alarm and visual indication that a ship or person is threatened by grave and imminent danger and requests immediate assistance. These automatic systems contain sufficient information in the distress alert message to identify the vessel, prepare to assist and begin a search. However, except when transmitted via satellite EPIRB, the distress alert is just the initial call for help. Communication between the vessel or person in distress and the Rescue Coordination Center (RCC) or ship assisting should always follow.

Distress Traffic: Distress traffic consists of a11 messages relating to the immediate assistance required by a person, ship, aircraft, or other vehicle in distress, including search and rescue communications and on­ scene communications.

District Commander: An officer of the U.S. Coast Guard designated by the Commandant to command all Coast Guard activities within a Coast Guard District. Coast Guard Districts are described in 33 CFRpart2.

Document of Continuity: A document issued by the Coast Guard to seafarers who are unwilling or otherwise unable to meet the requirements of 46 CFR §10.227, for the sole purpose of maintaining an individual’s eligibility for renewal of an endorsement.

Documented Alterations: Means changes to the vessel that is reflected in the approved stability information carried on board the vessel.

Dog: A pawl; a device applied to the winch drum to prevent rotation. See “On the dog.”

Dog House: A box structure to house bridge and/or towing winch controls. 

Domestic Voyage: A voyage from one United States port to another United

States port, without entering waters under the jurisdiction of another country unless the United States has entered into a treaty or an agreement with that country respecting mutual recognition of national mariner qualifications. This includes a voyage to nowhere that returns to the originating port.

Down flooding: Means, except as provided in 46 CFR §l 74.03S(b), the entry of seawater through any opening into the hull or superstructure of an undamaged vessel due to heel, trim, or submergence of the vessel.

Down Flooding Angle: Means, except as specified by 46 CFR §l 71.055(f), § l 72.090(d),

§173.095(e), §174.0lS(b), and §174.035(b)(2) of this chapter, the static angle from the intersection of the vessel’s centerline and waterline in calm water to the first opening that cannot be closed watertight and through which down flooding can occur.

Draft: The vertical distance from the molded baseline amidships to the waterline.

Drag: Forces opposing direction of motion due to friction, profile, and other components.

Drift Rate: The motion of a vessel caused by the action of the wind, the sea, and the current.

Drogue: A device used to slow rate of movement, usually towed or attached astern of the vessel.

Drug Test: A chemical test of an individual’s urine for evidence of dangerous drug use.

Drum: A cylindrical barrel, either of uniform or tapering diameters, on which rope is wound either for operation or storage; its surface may be smooth or grooved.

Dual-Mode Integrated Tug: An integrated tug barge (ITB) involving an articulated Barge (flexible) coupling system where the towing unit rolls and heaves (articulates) about a horizontal pivot point. Dual mode units resemble a conventional tug and are capable of towing in other configurations (astern or alongside).

Dutch Bar: A tow span type used primarily with hawsers.

Dye-Penetrant Test: An inspection method used to detect weld surface discontinuances.

Dynamic Load: Relating to energy or physical force in motion; as opposed to static load, a force producing motion or change.

Dynamic Tension: Resistance of the ship to be towed, the tow hawser, and the vertical component of wire catenary. This resistance cannot be accurately predicted.

Eductor: A pumping device, which uses the flow of water through a restriction to create a reduced pressure and cause the flow of water out of a space or compartment.

EIPS Wire: Extra Improved Plow Steel wire.

Elastic Stretch: The elongation of a wire rope or synthetic line caused by the deformation of the material during loading.

Electro-Technical Officer: An officer qualified in accordance with the provisions of Regulation IW6 of the STCW Convention.

Electro-Technical Rating: A rating qualified in accordance with the provisions of Regulation III/7 of the STCW Convention.

Embarkation Ladder:  A ladder provided at survival craft embarkation stations to permit safe access to survival craft after launching.

Embarkation Station: The place where a survival craft is boarded.

Emergency Position Indicating Radio Beacon (EPIRB) Station: A station in the maritime mobile service the emissions of which are intended to facilitate search and rescue operations.

Employment Assigned To: Means the total period of time a person is assigned to work on MODUs, including time spent ashore as part of normal crew rotation.

End Link: The last link in a length of chain.

Endorsement: Is a statement of a mariner’s qualifications and, for the purposes of this chapter, includes only those endorsements listed in §10.109 of 46 CFR subchapter B.

Engine Department: The department aboard a ship responsible for the main propulsion and auxiliary systems, and other mechanical, electrical, hydraulic, and refrigeration systems, including deck machinery and cargo-handling equipment.

Engine Room: The enclosed area where any main-propulsion engine is located. It comprises all deck levels within that area.

Entry-Level Crewmembers: Are all members of the crew not required to be licensed or to hold

an MMD endorsed as able seaman or qualified member of the engine department

Entry-Level Mariner: A mariner ho]ding no rating other than ordinary seaman, wiper, steward’s department, or steward’s department food handler (F.H.).

Environmental Communications: Broadcasts of information about the environmental conditions in which vessels operate, i.e., weather, sea conditions, time signals adequate for practical navigation, notices to mariners, and hazards to navigation.

Evaluation: Processing an application, from the point of receipt to approval or denial of the application, including review of all documents and records submitted with an application as well as those obtained from public records and databases.

Existing Vessel: A vessel, which is not a new vessel.

Existing Sailing School Vessel: A sailing vessel whose keel was laid prior to January 9,

1986, which has an application for initial inspection for certification as a sailing school vessel on file with the Coast Guard prior to January 9, 1987, and whose initial inspection for certification is completed prior to January 9, 1988.

Explosion Proof: Means electrical equipment approved as meeting UL 1203.

Exposed Waters: Waters more than 20 nautical miles (37 kilometers) from the mouth of a harbor of safe refuge and other waters which the Officer in Charge, Marine Inspection determines to present special hazards due to weather or other circumstances.

Extended-Size Lifejacket: A lifejacket that is approved for use by adults as well as by some larger children.

Extreme Towline Tension: The additive accumulation of the complex dynamic responses of

tug, tow, and towline.

Eye Splice: A loop formed in the end of a line by tucking the strand ends over and under the strands of the standing part of the rope. A thimble is often used in the eye.

Fails a Chemical Test for Dangerous Drugs: Means that the result of a chemical test conducted under 49 CFRpart 40 was reported as “positive” by a Medical Review Officer because the chemical test indicated the presence of a dangerous drug at a level equal to or exceeding the levels established in 49 CFRpart40.

Fairlead: Metal fittings which lead lines in a desired direction. A guide for a mooring line which enables the line to be passed through the ship’s bulwark or other barrier (See also chock), or to change direction through a congested area without snagging or fouling.

Fairlead (Roller) Chock: A chock with a roller(s) installed to lead a line to a bitt or cleat.

Fake (Faked Down): To lay out a line lengthwise in long, flat bights, so that when needed, it will pay out freely.

Fantail: The open deck area or topside overhanging part of the deck at the stem of a ship.

Fatigue: The tendency for materials or devices to break under repeated (cyclic) loading.

Federal On-Scene Coordinator: A Federal On-Scene Coordinator designated in the National Contingency Plan.

Fenders: Energy-absorbing materials or devices used to reduce contact between vessels.

Ferry: Means a vessel as described in§ 70.10-1 of his 46 CFR §199.30.

Fetch: The distance a wind blows over the sea surface without a significant change of direction. A factor in the buildup of waves.

Fiber Core: Cord or synthetic fiber used as the axial member of a rope.

Fidley: Upper Engine Room.

Fillet Weld: A weld that has a triangular cross section, joining two surfaces that are perpendicular to each other.

Final Report (FR): A vessel must report its name and position:

1. On arrival at its destination; or
2. When leaving a VTS area.

First Assistant Engineer: The engineer officer next in rank to the chief engineer and upon whom the responsibility for the mechanical propulsion and the operation and maintenance of the mechanical and electrical installations of the vessel will fall in the event of the incapacity of the chief engineer.

Fish Hooks: Outer wires of wire rope that break and cause short ends to project from the rope; a sign of wire rope deterioration.

Fish Plate: See “flounder plate”.

Fitting: Specially designed pieces on a ship’s deck used to control or secure a line or rope (e.g., chock, bitts, padeye, etc.).

Fixed Fire-Extinguishing System: Means-

1. A carbon dioxide system that satisfies 46 CFR §76.15 and the system labeling requirements in 46 CFR §78.47-9 and §78.47-11 and that is approved by the Commandant;
2. A manually-operated clean-agent system that satisfies the National Fire Protection Association (NFPA) Standard 2001 (incorporated by reference in §27.102) and is approved by the Commandant; or
3. A manually-operated water-mist system that satisfies NFPA 750 (incorporated by reference; see §27.102) and that is approved by the Commandant; or
4. A clean agent system that satisfies 46 CFR §95.16 and the labeling requirements of 46 CFR §97.37-9 and §97.37-1 I and that is approved by the Commandant.

Flame Arrester: Any device or assembly of a cellular, tubular, pressure, or other type used for preventing the passage of flames into enclosed spaces.

Flame Screen: A fitted single screen of corrosion-resistant wire of at least 30 by 30 mesh, or two fitted screens, both of corrosion-resistant wire, of at least 20 by 20 mesh, spaced not less than 1/2 inch or more than I l;2 inches apart.

Flammable and Inflammable: These words are interchangeable or synonymous terms for the purpose of the regulations in 46 CFR § 30.10-21.

Flammable Liquid: Any liquid which gives off flammable vapors (as determined by flashpoint from an open-cup tester, as used for test of burning oils) at or below a temperature of 80 °F. Flammable liquids are referred to by grades as follows:

1. Grade A. Any flammable liquid having a Reid 1 vapor pressure of 14 pounds or more. 1 American Society for Testing Materials Standard D 323 (incorporated by reference, see §30.01-3), Method of Test for Vapor Pressure of Petroleum Products (Reid Method).
2. Grade B. Any flammable liquid having a Reid 1 vapor pressure under 14 pounds and over 8112 pounds.
3. Grade C. Any flammable liquid having a Reid 1 vapor pressure of 8112 pounds or less and a flashpoint of 80 °F. or below.

Flashpoint: Indicates the temperature in degrees Fahrenheit at which a liquid gives off a flammable vapor when heated in an open-cup tester. For the purpose of the regulations in this 46 CFR § 30.10-27, flashpoints determined by other testing methods will be equivalent to those determined with an open-cup tester, as follows: TABLE 30.10-27: Equivalent Flashpoints (in F).

  Fleet Radio Station License: An authorization issued by the Commission for two or more ships

Having a common owner or operator.

Fleeting-Area: A separate location where individual barges are moored or assembled to make a tow. The barges are not in transport, but are temporarily marshaled, waiting for pickup by different vessels that will transport them to various destinations. A fleeting-area is a limited geographic area.

Float-Free Launching: A method of launching a survival craft or lifesaving appliance whereby the craft or appliance is automatically released from a sinking vessel and is ready for use.

Flounder Plate: A triangular steel plate to which bridle legs are connected, sometimes called “fish plate.”

Flounder Plate, Fish Plate, Tow(ing) Plate: A heavy triangular steel plate with reinforced or bushed holes in each corner that can accept the pin of a towing shackle. Most commonly used as the connecting point for the two legs of a towing bridle and the towing pendant or chain. May also be used in the makeup of a tandem tow utilizing an underrider. Some tow plates have an extra hole that can be used to shackle in a bridle retrieving wire for hauling up the bridle.

Foam: A fire-extinguishing agent that is a fluid aggregate of small air filled bubbles that will float on the surface of most flammable liquids. It is formed by mixing foam concentrate with water (foam solution), and then agitating it with air, which causes it to expand.

Foam Concentrate: An aqueous solution of concentrated liquid (usually protein-base) with a stabilizer added which, when mixed with water and air, forms a fire extinguishing foam that is highly resistant to breakdown.

Foam Solution: A homogeneous solution of foam concentrate in water. The term “water rate” is used in the Coast Guard regulations; its meaning is synonymous with that of “foam solution rate” for 3% and 6% concentrate systems.

Fore Deck: Forward of the amidships portion of a vessel.

Fore Peak: Void space (could be used for ballast) located forward of the collision bulkhead.

Forecastle: Raised foreword section of a vessel’s weather deck. This area contains most of the ship’s deck machinery and tow fittings.

Foreign Vessel: A vessel of foreign registry or operated under the authority of a country except the United States.

Foreign Voyage: A voyage involving a vessel:

1. Arriving at a place under the jurisdiction of the United States from a place in a foreign country;
2. Making a voyage between places outside of the United States;
3. Departing from a place under the jurisdiction of the United States for a place in a foreign country; or
4. Making a voyage between a place within a territory or possession of the United States and another place under the jurisdiction of the United States not within that territory or possession. The Commonwealth of Puerto Rico is considered to be a “territory or possession” of the United States, so a voyage between Miami, FL and San Juan, PR is a foreign voyage. For the purposes of this enclosure, a Great Lakes voyage is not a foreign voyage, even if the vessel stops at a port in Canada. In addition, if a vessel engages on both domestic and foreign voyages, the requirements for vessels “engaged on foreign voyages” apply. Also, see the related definition for “international voyage .”

Forward Hold: Storage area aft of the fore peak.

Free-Fall Launching: The method of launching a survival craft whereby the craft, with its full complement of persons and equipment on board, is released and allowed to fall into the sea without any restraining apparatus.

Free-Running Speed: Maximum speed of a tug without a tow.

Free-Spooling: To pay out scope by releasing the brake and allowing the towing drum to rotate as a result of the drag of the tow, with the tow motor disengaged.

Freeboard: Distance from the weather deck to the waterline.

Freeing Ports: Openings built into bulwarks to allow the egress of water.

Freight Vessel: A motor vessel of more than 15 gross tons as measured under section 14502 of 46 USC §2101 , or an alternate tonnage measured under section 14302 of 46 USC §2101 as prescribed by the Secretary under section 14104 of 46 USC §2101 that carries freight for hire, except an oceanographic research vessel or an offshore supply vessel.

Freshening the Nip: Paying out or hauling in the tow wire to move the contact point in order to distribute wear on the hawser, stern roller, towing bows, H-bitts, winch drum, etc.

Frictional Resistance: The force created by an object as it moves through a fluid such as water or air.

Fuse Pendant: A pendant of wire rope or chain specifically designed to fail at a known tension. May be used to protect the rest of the rigging arrangement. Also called a “weak link.”

Gallery: A platform located between the engine room and fidley. 

Galley: Nautical name for kitchen.

Garbage: All kinds of food wastes, domestic wastes and operational wastes, plastics, cargo residues, cooking oil, fishing gear, and animal carcasses generated during the normal operation of the ship and liable to be disposed of continuously or periodically except those substances which are defined or listed in other Annexes to the present Convention.

Gas Free: Means free from dangerous concentrations of flammable or toxic gases.

Gate Lines: Independent lines utilized for towing astern to facilitate adjustments individually.

Gauging: The only practical way of determining the degree of deterioration is to measure the thickness of the member in question and compare it with the original thickness. Thickness measurements can be made by drilling and gauging or by ultrasonic measurement, the term gauging is meant to include both methods of measurement. There are two approaches to gauging. First, gauging is used to provide a quantitative basis for evaluating a questionable local condition. Second, Belt gauging goes beyond the investigating of a local condition. It involves taking readings around several complete transverse sections of the hull including deck, sides and bottom.

General Rules and Regulations: Means the requirements contained in this chapter.

GM: See “Metacentric height.”

Gob Line: Line used lo secure the towline aft over the centerline of a tug.

Grapnel: A small, four-armed anchor used mainly to recover objects in the water. This device may also be helpful in establishing a method of boarding a vessel without assistance from the deck.

Great Lakes: For the purpose of calculating service requirements for an endorsement, means the Great Lakes and their connecting and tributary waters, including the Calumet River as far as the Thomas J. O’Brien Lock and Controlling Works (between miles 326 and 327), the Chicago River as far as the east side of the Ashland Avenue Bridge (between miles 321 and 322), and the Saint Lawrence River as far east as the lower exit of Saint Lambert Lock. For purposes of requiring MMCs with rating endorsements, the connecting and tributary waters are not part of the Great Lakes.

Great Lakes Barge: A non-self-propelled vessel of at least 3,500 gross tons as measured under section 14502 of 46 USC §210 I , or an alternate tonnage measured under section 14302 of 46 USC §2101 as prescribed by the Secretary under section 14104 of 46 USC §2101 operating on the Great Lakes.

Great Lakes Voyage: A voyage on the Great Lakes, where the Great Lakes are defined as the Great Lakes of North America and the St. Lawrence River west of a rbumb line drawn from Cap Des Rosiers to West Point, Anticosti Island, and, on the north side of Anticosti Island, the meridian of longitude 063 degrees West.

Grommet: An endless circle or ring fabricated from one continuous length of strand or rope.

Gross Register Tons or GRT: The gross ton measurement of the vessel under 46 U.S.C. chapter 145, Regulatory Measurement.

Gross Tonnage or GT: The gross tonnage measurement of the vessel under 46 U.S.C. chapter 143, Convention Measurement.

Gross Tonnage: This refers to the gross tonnage assigned under the International Tonnage Convention measurement system.

Gross Tons: The tonnage determined by the tonnage authorities of a vessel’s flag state in accordance with the national tonnage rules in force before the entry into force of the International Convention on Tonnage Measurement of Ships, 1969 (“Convention”). For a vessel measured only under Annex I of the Convention, gross tons means that tonnage. For a vessel measured under both systems, the higher gross tonnage is the tonnage used for the purposes of the 300-gross-ton threshold.

Ground Tackle: General term for all anchoring equipment aboard ship.

Gypsy Head: (See warping head).

H-bitt: Reinforced vertical steel posts with substantial horizontal structure (caval) mounted to the vessel and used to lead or stop off a tow hawser; a hard point used for towing.

Hairpin: A metal pin, which is used to secure detachable link.

Harbor Assist: The use of a towing vessel during maneuvers to dock, undock, moor, or unmoor a vessel, or to escort a vessel with limited maneuverability.

Harbor Tugs: Vessels that perform harbor assists.

Hatch: Access opening in the deck of a vessel, fitted with a hatch cover for watertight closure.

Hawse Pipe: Heavy casting through which the anchor chain runs from deck down and forward through ship’s bow plating.

Hawser: Main Hawser- A line (generally nylon) used as the primary towing medium on tugs not equipped with tow winches (Hawser boats). Length and line size varied depending on horsepower of the tug, size of tow and areas of operation. Intermediate hawser­ A line (generally nylon) hawser used in the make up of multiple tows by connecting from the stem of the lead barge to the bow of the following barge. Intermediate hawsers were usually in the vicinity of 600 feet in length depending on the size of the tug, tow and intended operating area.

Hazardous Condition: Any condition that may adversely affect the safety of any vessel, bridge, structure, or shore area or the environmental quality of any port, harbor, or navigable waterway of the United States. It may, but need not, involve collision, allision, fire, explosion, grounding, leaking, damage, injury or illness of a person aboard, or manning-shortage.

Hazardous Material: A liquid material or substance that is­

1. flammable or combustible;
2. designated a hazardous substance under section 311(b) of the Federal Water Pollution Control Act (33 U.S.C. I 321); or
3. designated a hazardous material under section 5103(a) of title 49.

Hazardous Substance: Any substance designated pursuant to subsection (b)(2) of 33 u.s.c. §1321.

Hazardous Vessel Condition: Any condition related to a vessel’s ability to safely navigate Operating maneuver, and includes, but is not limited to:

1. The absence or malfunction of vessel operating equipment, such as propulsion machinery, steering gear, radar system, gyrocompass, depth sounding device, automatic radar plotting aid (ARPA), radiotelephone, Automatic Identification System equipment, navigational lighting, sound signaling devices or similar equipment.
2. Any condition on board the vessel likely to impair navigation, such as lack of current nautical charts and publications, personnel shortage, or similar condition.
3. Vessel characteristics that affect or restrict maneuverability, such as cargo or tow arrangement, trim, loaded condition, underkeel or overhead clearance, speed capabilities, power availability, or similar characteristics, which may affect the positive control or safe handling of the vessel or the tow.

Head: Nautical name for bathrooms.

Headed Fair: An expression meaning bearing toward an object or an area. In towing, this refers to the tow bearing in the same direction as the tug. 

Headquarters: Means the Office of the Commandant, United States Coast Guard, Washington, DC.

Hearing Protector Device: A device worn to reduce the )eve) of noise heard by the wearer; hearing protective device (HPD).

Heave: Vertical displacement of a ship in a seaway, as distinct from pitching, which is essentially a rotation about an athwartships axis. Heave generally refers to an upward movement, bodily, of the entire ship. Also, to haul in or retrieve a line or rope.

Helix: The twist or curvature of the individual strands of a wire rope.

High Consequence Cargo: Any cargo that is a:

1. Division l.l or 1.2 explosive as defined in 49 CFR 1§73.50 and that is in a quantity in excess of 5,000 kg net explosive weight;
2. Division 2.3 gas as defined in 49 CFR 1§72.101 that is a material poisonous by inhalation as defined in 49 CFR 171.8 and that is in a quantity in excess of 10,000 kg;
3. Division 6.1 liquid as defined in 49 CFR 172.101 that is a material poisonous by inhalation as deemed in 49 CFR §171.8 and that is in a quantity in excess of 30,000 kg;
4. Class 7 radioactive material that is a highway route controlled quantity or fissile material, controlled shipment, as defined in 49 CFR 173.403;
5. Division 1.5 compatibility group D explosive material for which a permit is required under 49 CFR §176.415, and that is in a quantity in excess of 40,000 kg;
6. Bu)k liquid cargo that is required to be carried in a Type I ship or cargo containment system due to safety hazards under 46 CFR§153; or
7. Bulk liquefied gas cargo that is flammable and/or toxic and carried under 46 CFR .

High Line: A single line rigged between two ships underway transferring stores.

High-Speed Craft Type Rating (HSC): An endorsement for specific duty on a particular type and model of high-speed craft (compliant with the high-speed craft code).

Hackle: Kinking of one or more strands of twisted fiber line or wires on a wire rope.

Hog (Hogging): Deviation of the keel from a straight line, in which the keel is convex upward.

Honolulu Tow: Not used commercially and has been replaced by the use of double drum winches on tugs (See “tandem tow”).

Hookup: The process of making up the connections to tow a vessel.

Horizontal Stern Rollers: A large-diameter roller, set in the stem bulwarks on the centerline and faired to the caprail. Provides a minimum chafe point for the tow wire during heave-in and payout.

Horsepower or HP: Means, for the purpose of 46 CFR § I0.107 subchapter B , the total maximum continuous shaft horsepower of the entire vessels main propulsion machinery as determined by the manufacturer. This term is used when describing a vessel’s propulsion power and also when placing limitations on an engineer officer license or endorsement. One horsepower equals 0.75 kW.

Horsepower, Brake: The power delivered at the engine’s shaft.

Horsepower, Indicated: Power measured in diesel engine cylinders by means of an instrument (the “indicator”), which continuously records the steam or gas pressure throughout the length of the piston travel.

Horsepower, Shaft: Power transmitted through the shaft to the propeller. It is usually measured aboard the ship as close to the propeller as possible by means of a torsion meter. The power actually delivered to the propeller is somewhat less than that measured by the torsion meter.

Hummock: An irregular ridge or hillock on sea ice.

Hydrodynamic Resistance: The force exerted by the motion of fluids upon a body immersed

in the fluid. As applied to towing: the resistance created by water as a body moves through it.

IECEx System: An international certification system covering equipment that meets the provisions of the IEC 60079 series of standards. The IECEx system is comprised of an Ex Certification Body and Ex Testing Laboratory that has been accepted into the IECEx System after satisfactory assessment of their competence to ISO/IEC Standard 17025, ISO/IEC Guide 65, IECEx rules of procedures, IECEx operational documents, and IECEx technical guidance documents as part of the IECEx assessment process.

Immersion suit: A protective suit that reduces loss of body heat of a person wearing it in cold water.

In Irons: An expression used by ship handlers to indicate limited control in maneuvering the ship. In towing, this can be caused by a tow wire that is “captured” at the stem, reducing the effect of the rudder of the tug.

In Step: An expression used to indicate that the towing ship and its tow are each riding the crests and troughs of waves simultaneously.

Increase in Scope: Means additional authority added to an existing credential, such as adding a new route or increasing the authorized horsepower or tonnage.

Independent laboratory: A laboratory that is accepted by the Commandant under 46 CFR Part 159 for the testing and listing or certification of electrical equipment.

Inflatable Appliance: An appliance that depends upon non-rigid, gas-filled chambers for buoyancy and that is normally kept un-inflated until ready for use. 

Inflated Appliance: An appliance that depends upon non-rigid, gas-filled chambers for buoyancy and that is kept inflated and ready for use at all times.

Inland Waters of the United States: The waters lying inside the baseline United States from which the territorial sea is measured and those waters outside such baseline which are a part of the Gulf lntracoastal Waterway. 

Inland Oil Barge: A non-self-propelled vessel carrying oil in bulk as cargo and certificated to operate only in the inland waters of the United States, while operating in such waters.

Inland Towing: Point-to-point towing performed on inland waterways such as nvers.

Inland Waters: The navigable waters of the United States shoreward of the Boundary Lines as described in part 7 of this chapter, excluding the Great Lakes, and, for towing vessels, excluding the Western Rivers.

Inspection: An examination to detect the presence of prohibited weapons, dangerous substances and devices that could be used in an unlawful act threatening the security of a vessel, port, or waterfront facility.

Integral Tank: A tank that is a structural part of the vessel’s hull and is influenced in the same manner and by the same loads that stress the adjacent hull structure.

Integrated Tug Barge or ITB: Any tug barge combination which, through the use of special design features or a specially designed connection system, has increased sea keeping capabilities relative to a tug and barge in the conventional pushing mode. An ITB can be divided into either a dual-mode 1TB or a push-mode ITB. The definitions for those categories can be found elsewhere in this section.

International Tonnage Certificate (1969): An International Tonnage Certificate (1969) is an internationally recognized document used to certify tonnages and dimensions of vessels flying flags of nations, which are party to the International Convention on Tonnage Measurement of Ships, 1969. The certificate is issued for vessels 79 feet and over in convention length that engage on foreign voyages. The certificate must be carried on board any U.S. flag vessel (whether self-propelled or not) that is greater than 79 feet in convention length and that is engaged on a foreign voyage.

Intercontinental Voyage: A voyage between a country to which SOLAS applies and a port outside that country. A country, as used in this definition, includes every territory for the international relations of which a contracting government to the convention is responsible or for which the United Nations is the administering authority. For the U.S., the  term “territory” includes the Commonwealth  of Puerto Rico, all possessions of the United States, and all lands held by the United States under a protectorate or mandate. For the purposes of this subchapter, vessels are not considered as being on an “international voyage” when solely navigating the Great Lakes and the St. Lawrence River as far east as a straight line drawn from Cap des Rosiers to West Point, Anticosti Island and, on the north side of Anticosti Island, the 63rd meridian.

Intrinsically Safe: Means a protection technique for electrical equipment meeting the requirements specified in 46 CFR §111.105-11.

Invalid Credential: Means an MMC, MMD, license, STCW endorsement, or Certificate of Registry that has been suspended or revoked, has expired, has been tampered with, has not been signed, or has been superseded in accordance with §10.205 of 46 CFR §10.107 subchapter B.

IWRC: Independent wire rope core. A wire rope used as the axial member of a larger wire rope.

Jack Stay: Wire or line rigged for a special purpose, such as hanging sea bags.

Jacob’s Ladder: Portable ladder, with rope or wire sides and wooden rungs, slung over the side for temporary use.

Jam Nuts: A second nut installed hard against the first nut to prevent rotary motion of the first nut.

Jaw Width: The dimension of the opening between the eyes of a shackle.

Keel Laying Date: The date upon which progressive construction identifiable with a specific vessel begins, including construction of the first module or prefabricated section of the hull that is identifiable with that vessel.

Kenter Detachable Link: A type of connection normally used to join two pieces of stud link or cast chain. See “detachable link.”

Kilowatt or kW: Means 11/3 horsepower. This term is used when describing a vessel’s propulsion power and also when placing limitations on an engineer officer license or endorsement.

Kink: A unique deformation of a wire rope caused by a loop of rope being pulled down tight. It represents irreparable damage to and an indeterminate loss of strength in the rope.

Kort Nozzle: A nozzle used to enclose the propeller of a ship as a means of boosting power.

Lakes, Bays, and Sounds: Under this designation shall be included all tank vessels navigating the waters of any of the lakes, bays, or sounds other than the waters of the Great Lakes.

Large Passenger Vessel: For the purposes of subpart Hof I 2 46 CFR §10.107 subchapter B, and part 15, means a vessel of more than 70,000 gross tons, as measured under 46 U.S.C. 14302 and documented under the laws of the United States, with capacity for at least 2,000 passengers and a coastwise endorsement under 46 U.S.C. chapter 121.

Lateral Control Wire: An auxiliary wire used to limit the motion of the tow hawser in the athwartships direction.

Launching Appliance or Launching Arrangement: The method or devices designed to transfer a survival craft or rescue boat from its stowed position to the water. For a launching arrangement using a davit, the term includes the davit, winch, and falls.

Lay: The direction of the twist of strands of a rope.

Lay Length: The distance measured parallel to the axis of the rope (or strand) in which a strand (or wire) makes one complete helical revolution about the core (or center).

Layer: A single thickness, coat, fold, wrap, or stratum. In towing, wraps of wire around a towing winch are counted as layers.

Lazarette: A storage area located at the boats stem housing the steering gear.

Lazy Jacks: Small lines used to tend and recover the towline when rigging a recovery for a Liverpool bridle.

Leading Pendant: A length of chain or wire used between the tow and the towing hawser to ensure a safe distance during hookup and disconnect.

Lee: An area that is sheltered from the wind.

Leeward: Away from the wind.

Length: Means the distance between fore and aft points on a vessel. The following specific terms are used and correspond to specific fore and aft points:

1. Length between perpendiculars (LBP) means the horizontal distance measured between perpendiculars taken at the forward­ most and after-most points on the waterline corresponding to the deepest operating draft. For a small passenger vessel that has underwater projections extending forward of the forward-most point or aft of the after-most point on the deepest waterline of the vessel, the Commanding Officer, U.S. Coast Guard Marine Safety Center, may include the length or a portion of the length of the underwater projections in the value used for the LBP for the purposes of this subchapter. The length or a portion of the length of projections that contribute more than 2 percent of the underwater volume of the vessel is normally added to the actual LBP.
2. Length overall (LOA) means the horizontal distance between the forward-most and after-most points on the hull.
3. Length on the waterline (LWL) means the horizontal distance between the forward-most and after-most points on a specified deck measured along the deck, excluding sheer.
4. Load line length (LLL) has the same meaning that is provided for the term length in§ 42.13-15(a) of this chapter.
5. Mean length is the average of the length between perpendiculars (LBP) and the length on deck (LOD).

Length Between Perpendiculars (LBP): The horizontal distance measured between perpendiculars taken at the forward-most and after-most points on the waterline

corresponding to the deepest operating draft. For a small passenger vessel that has underwater projections extending forward of the forward-most point or aft of the after-most point on the deepest waterline of the vessel, the Commanding Officer, U.S. Coast Guard Marine Safety Center, may include the length or a portion of the length of the underwater projections in the value used for the LBP for the purposes of this subchapter. The length or a portion of the length of projections that contribute more than 2 percent of the underwater volume of the vessel is norma11y added to the actual LBP.

Length Of Tow: Means, when towing with a hawser, the length in feet from the stern of the towing vessel to the stem of the last vessel in tow. When pushing ahead or towing alongside, length of tow means the tandem length in feet of the vessels in tow excluding the length of the towing vessel.

Length Of Vessel: The load-line length defined in§ 42.13-15 (a) of this chapter.

Length On Deck (LOD): Means the length between the forward most and after-most points on a specified deck measured along the deck, excluding sheer.

Length On The Waterline (LWL): Means the horizontal distance between the forward-most and after-most points on a vessel’s waterline

Length Overall (LOA): The horizontal distance between the forward most and after-most points on the hull.

Level Wind: A device used during retrieval of a wire to move the wire along the length of the drum to allow it to be stored evenly on the drum of a towing machine.

License for Apprentice Mate (Steersman): Pertains to a mariner in training to become master or mate (pilot) of towing vessels, who has passed all required examinations for the applicable towing license. Nonetheless, he or she may only serve under the direct supervision of an officer qualified for towing vessels.

License for Master of Towing Vessels: Authorizes service within any route authorized by the license, including harbor assist and limited local area.

License for Master of Towing Vessels, Limited: Allows a mariner with limited geographic experience an opportunity to obtain a license. This will authorize service only in limited geographic areas. 

License for Mate (Pilot) of Towing Vessels: Pertains to a qualified officer subordinate to a master of towing vessels. A mate (pilot) of towing vessels may stand a watch, but a master of towing vessels must also be on the vessel.

Lifeboatman Limited: A mariner who is qualified to take charge of, lower, and operate life rafts, rescue boats, and other survival equipment on vessels where lifeboats are not installed.

Lifejacket: A flotation device approved as a life preserver or lifejacket.

Lighter: To use a boat or barge to service larger ships in harbors, or to remove fuel or cargo from a stricken vessel.

Lightweight: Means the displacement of a vessel with fixed ballast and with machinery liquids at operating levels but without any cargo, stores, consumable liquids, water ballast, or persons and their effects.

Limited Geographic Area: A local area of operation, usually within a single harbor or

port. The local Captain of the Port (COTP) determines the definition of local geographic area for each zone.

Limited Local Area: Means a defined limited geographic area designated by the local OCMI.

Limited Local Area Route: Specific waterways or a section of one. Applying for a limited local area route provides the option of taking a simplified or limited examination. This recognizes that towing vessels do not always provide an opportunity to gain extensive experience on a specific route. Limited local area routes may not substitute for Near-Coastal routes or Ocean Routes.

Line: A term frequently applied to a fiber or synthetic rope, especially if it moves or is used to transmit a force.

Links: A connecting component of towing systems.

Liquefied Flammable Gas: Any flammable gas having a Reid vapor pressure exceeding 40 pounds, which has been liquefied.

Liquefied Gas or LG: Means a cargo that has a vapor pressure of 172 kPa (25 psia) or more at 37.8 °C (100 °F).

Liquefied Gas Tanker: Means a tank vessel that is certificated to carry or carries liquefied gases in bulk as cargo or cargo residue. For the purposes of qualifying for an STCW endorsement for advanced liquefied gas tanker cargo operations, this includes tank barges.

Liquefied Natural Gas: Natural gas (predominantly methane, CH4) that has been (LNG) converted to liquid form by cooling to approximately -258 degrees F (-161 degrees C) for ease of storage or transport. 

Liquid Cargo in Bulk: A liquid or liquefied gas listed in §153.40 of 46 CFR §10.107 subchapter Band carried as a liquid cargo or liquid­ cargo residue in integral, fixed, or portable tanks, except a liquid cargo carried in a portable tank actually loaded and discharged from a vessel with the contents intact.

Liverpool Bridle: A method of rigging a tow hawser; most commonly used in refloating a stranded ship. This method allows the tow vessel to head into the predominant set while still pulling the strand. 

Load Cell: An instrument for measuring tension or torque.

Load Line Length (LLL): Has the same meaning that is provided for the term Length in §42.13-15(a) of46 CFR §170.055.

Locking Pin (Keeper): Device used to hold or maintain a chain stopper, shackle, or other similar devices in a designated position.

Longitudinal: A term applied to the fore-and-aft frames of a ship. Generally, the fore-and-aft direction on a ship.

Lower level: Is used as a category of deck and engineer officer endorsements established for assessment of fees. Lower-level officer endorsements are other than those defined as upper level, for which the requirements are listed in subparts D, E, and G of part 11 of 46 CFR §10.107 subchapter B.

Machinery Space: Means any space that contains machinery and related equipment including Category A machinery spaces, propelling machinery, boilers, oil fuel units, steam and internal combustion engines, generators and centralized electrical machinery, oil filling stations, refrigeration, stabilizing, ventilation, and air conditioning machinery, and similar spaces and trunks to such spaces.

Main Deck (00): First deck above the waterline.

Main Transverse Watertight Bulkhead: Means a transverse bulkhead that must be maintained watertight in order for the vessel to meet the damage stability and subdivision requirements in 46 CFR §170.055.

Major Character: Any repair, alteration or modification to a vessel that is a major conversion as decided by Commandant (CG-CVC).

Major Conversion: A conversion of a vessel that:

1. Substantially changes the dimensions or carrying capacity of the vessel;
2. Changes the type of the vessel;
3. Substantially prolongs the life of the vessel; or
4. Otherwise so changes the vessel that it is essentially a new vessel, as decided by the Secretary.

Management Level: The level of responsibility associated with:

1. Serving as master, chief mate, chief engineer officer or second engineer officer onboard a seagoing ship; and
2. Ensuring that all functions within the designated area of responsibility are properly performed.

Marine Chemist: A person certificated by the National Fire Protection Association as a marine chemist.

Marine Environment: Means-

1. The navigable waters of the United States and the land and resources in and under those waters;
2. The waters and fishery resources of an area over which the United States asserts exclusive fishery management authority.

Marine Evacuation System: An appliance designed to rapidly transfer large numbers of persons from an embarkation station by means of a passage to a floating platform for subsequent embarkation into associated survival craft, or directly into associated survival craft.

Marine Inspector or Inspector:  Any person from the civilian or military branch of the Coast Guard assigned under the direction of an Officer in Charge, Marine Inspection, or any other person designated to perform duties related to the inspection, enforcement, and administration of Subtitle II, Title 46 U.S. Code; Title 33 U.S. Code; and regulations issued under these statutes.

Maritime Mobile Service: An international system for the identification of radio stations in Identities (MMSI) the maritime mobile service. The system is comprised of a series of nine digits, which are transmitted over the radio path to uniquely identify ship stations, ship earth stations, coast stations, coast earth stations and groups of stations.

Maritime Radio Determination Service: A maritime radio communication service for determining the position, velocity, and/or other characteristics of an object, or the obtaining of information relating to these parameters, by the propagation properties of radio waves.

Maritime Security (MARSEC) Level I: The new maritime security normalcy. This is the level of threat potential for which protective measures may be maintained for an indefinite period of time; in other words, these are the normal, every day security measures.

Maritime Security  (MARSEC) Level II: Means there is a heightened threat of an unlawful act against a port, waterfront facility, or vessel and intelligence indicates that terrorists are likely to be active within a specific area or against a specific class of target. This risk level indicates that a particular segment of the industry may be in jeopardy, but that no specific target has been identified. Additional protective measures may be expected to be sustained for substantial periods of time.

Maritime Security (MARSEC) Level III: Means the threat of an unlawful act against a port, waterfront facility, or vessel is probable of imminent. Intelligence may indicate that terrorist have chosen specific targets, though it may not be possible to identify such targets. Additional protective measures are not intended to be sustained for substantial periods of time.

Maritime Support Station: A station on land used in support of the maritime services to train personnel and to demonstrate, test and maintain equipment.

Master: The officer having command of a vessel.

Master of Towing Vessels: Authorizes service within any route authorized by the license,

including harbor assist and limited local area.

Master of Towing Vessels, Limited: Means a license to operate a towing vessel of less than 200 gross tons limited to a local area within the Great Lakes, inland waters, or Western Rivers designated by the Officer in Charge, Marine Inspection (OCMI).

Mate: A qualified officer in the deck department other than the master.

Mate (Pilot) of Towing Vessels:Pertains to a qualified officer subordinate to a Master Vessels. A Mate (Pilot) of TVs may stand a watch, but a Master of TVs must also be on the vessel.

Mean Length: Is the average of the length between perpendiculars (LBP) and the length on deck (LOD).

Medical Certificate: A certificate issued by the Coast Guard under 46 CFR part 10, subpart C that serves as proof that the seafarer meets the medical and physical standards for merchant mariners.

Merchant Marine Officer: The term “merchant marine officer” means an individual issued a license by the Coast Guard authorizing service as:

1. A master, mate, or pilot on a documented vessel that:
2. Is of at least 1,000 gross tons as measured under section 14502 of NTG 10.9.2011 or an alternate tonnage measured under section 14302 of NTG 10.9.2011 as prescribed by the Secretary under section 14104 of NTG 10.9.2011 ; and
3. Operates on the oceans or the Great Lakes; or
4. An engineer officer on a documented vessel propelled by machinery of at least 4,000 horsepower.

Merchant Mariner Credential or MMC: A credential issued by the Coast Guard under 46 CFR part 10. It combines the individual Merchant Mariner’s document, license, and certificate of registry enumerated in 46 U.S.C. subtitle II part E as well as the STCW endorsement into a single credential that serves as the mariner’s qualification document, certificate of identification, and certificate of service.

Mess: Crewmember eating area.

Messenger: A light line used for hauling over a heavier rope or hawser.

Metacenter: The imaginary point through which the force of buoyancy acts for small angles of heel.

Metacentric Height (GM): Distance between the metacenter and the center of gravity of a ship; a measure of stability.

Minimum Bend Radius: The safe minimum radius for a given diameter, material, and method of bending. Bends of less than this radius may cause damage to the rope or line.

MMC Application: The application for the MMC, as well as the application for any endorsement on an MMC.

Mobile Offshore Drilling: A vessel capable of engaging in drilling operations for the Unit or MODU exploration for or exploitation of subsea resources. MODU designs include the following:

1. Bottom bearing units, which include:
2. Self-elevating (or jack-up) units with moveable, bottom
3. bearing legs capable of raising the hull above the surface of the sea; and
4. Submersible units of ship-shape, barge-type, or novel hull design, other than a self-elevating unit, intended for operating while bottom bearing.
5. Surface units with a ship-shape or barge-type displacement hull of single or multiple hull construction intended for operating in a floating condition, including semi-submersibles and drill ships.

Moment Ann: The perpendicular distance from the point of application of a rotational force to the line of action of the force. 

Month: Means 30 days, for the purpose of complying with the service requirements of this subchapter.

Mortise: The opening of a shackle or detachable link. The inside dimension, measured across the opening of a shackle or detachable link.

Motor Vessel: Any vessel more than 65 feet in length, which is propelled by machinery other than steam.

Motorboat: Means any vessel indicated in column five of table 24.05-l(a) in 46 CFR §24.05-1, 65 feet in length or less, which is equipped with propulsion machinery (including steam). The length must be measured from end-to-end over the deck, excluding sheer. This term includes a boat equipped with a detachable motor. For the purpose of this subchapter, motorboats are included under the term vessel, unless specifically noted otherwise.

The various length categories of motorboats are as follows:

1. Any motorboat less than 16 feet in length.
2. Any motorboat 16 feet or over and less than 26 feet in length.
3. Any motorboat 26 feet or over and less than 40 feet in length.
4. Any motorboat 40 feet or over and not more than 65 feet in length.
5. The expression “length must be measured from end-to-end over the deck excluding sheer” Means a straight-line measurement of the overall length from the foremost part of the vessel to the aftermost part of the vessel, measured parallel to the centerline. Bowsprits, bumpkins, rudders, outboard motor brackets, and similar fittings or attachments, are not to be included in the measurement. Length must be stated in feet and inches.

MPI (Magnetic Particle Inspection): A nondestructive test, using a magnetic field and steel filings or particles to locate and define flaws in steel structures.

Muster Station: The place where persons on board assemble before boarding a survival craft.

National Contingency Plan: Means the National Contingency Plan prepared and published

under subsection (d) of 33 U.S.C. §1321.

National Driver Register or  NDR: The nationwide repository of information on drivers maintained by the National Highway Traffic Safety Administration under 49 U.S.C. chapter 303.

National Maritime Center Detachments: A Coast Guard office that supports the National Maritime Center in the issuance of merchant mariners’ credentials and endorsements.

National Officer Endorsement: An annotation on an MMC that allows a mariner to serve in the capacities listed in §10.109(a) of 46 CFR. The officer endorsement serves as the license and/or certificate of registry pursuant to 46 U.S.C. subtitle II part E.

National Rating Endorsement: An annotation on an MMC that allows a mariner to serve in those capacities set out in 46 CPR §10.109(b) and (c) of this part. The rating endorsement serves as the merchant mariner’s document pursuant to 46 U.S.C. subtitle II part E.

National Response Unit: Means the National Response Unit established under subsection

(j) of 33 U.S.C. §1321.

Nationality: The state (nation) in which a person is a citizen or to which a person owes permanent allegiance.

Natural Gas Fuel Handling Room: Means any enclosed space where natural gas is pumped, compressed or processed. Examples of natural gas handling rooms include pump rooms, compressor rooms, and natural gas valve rooms

Natural Pivot Point: The location on a tug about which the tug turns in the horizontal plane. It is generally located on the centerline of the ship about one-third of the ship’s length from the bow.

Nautical School Vessel: A vessel operated by or in connection with a nautical school or an educational institution under section 558 of title 40 in the U.S.C.

Navigable Waters: Means all navigable waters of the United States including the territorial sea of the United States, extending to 12 nautical miles from United States baselines, as described in Presidential Proclamation No. 5928 of December 27, 1988.

Navigable Waters of the United States: Includes all waters of the territorial sea of the United States as described in Presidential Proclamation No. 5928 of December 27, 1988.

Navigable waters of the Means United States: Means the same as this term is defined in 33 CFR §2.36(a). This includes a 12-nautical-mile wide U.S. territorial sea as measured from the baseline, U.S. internal waters subject to tidal influence, and certain U.S. internal waters not subject to tidal influence.

Navigational Communications: Safety communications pertaining to the maneuvering of vessels or the directing of vessel movements. Such communications are primarily for the exchange of information between ship stations and secondarily between ship stations and coast stations.

NDR- Listed Convictions: A conviction of any of the following motor vehicle-related offenses or comparable offenses: 

1. Operating a motor vehicle while under the influence of, or impaired by, alcohol or a controlled substance; or
2. A traffic violation arising in connection with a fatal traffic accident, reckless driving, or racing on the highways.

Near-Coastal: Means ocean waters not more than 200 miles offshore from the U.S. and its possessions, except for MMCs endorsed as Operator of Uninspected Passenger Vessel for which near-coastal is limited to waters not more than 100 miles offshore from the U.S. and its possessions. This would also include those near-coastal waters identified by another Administration when the U.S. has entered into a treaty or an agreement with that country respecting the recognition of the U.S. near-coastal endorsement.

New Sailing School Vessel: Means a sailing school vessel, which is not an existing sailing school vessel.

New Vessel: 

1. For vessels, which require a Certificate of Inspection, a new vessel is a vessel, which has not received an initial Certificate of Inspection.
2. For vessels that do not require a Certificate of Inspection, a new vessel is a vessel, which has not received a Load Line assignment.

Nip: A sharp bend in a line or wire.

Nipping The Wire: To periodically adjust the scope of the wire to reduce the wear on any one point.

Non-Hazardous: Means an area in which an explosive gas atmosphere is not expected to be present in quantities that require special precautions for the construction, installation and use of electrical equipment.

Non-Resident Alien: For the purposes of subchapter Hof part 12, and part 15 of 46 CFR, means an individual who is not a citizen or alien lawfully admitted to the United States for permanent residence, but who is employable in the United States under the Immigration and Nationality Act (8 U.S.C. 1101 et seq.), including an alien crewman described in section lOJ(a)(J 5)(D)(i) of that Act who meets the requirements of 46 U.S.C. 8103(k)(3)(A).

Non-Selectable Transponder:  A transponder whose coded response is displayed on any conventional radar operating in the appropriate band.

Noncommercial Communications: Communication between coast stations and ship stations other than commercial transport ships, or between ship stations aboard other than commercial transport ships which pertain to the needs of the ship.

Non-tank Vessel: A self-propelled vessel that:

1. Is at least 400 gross tons as measured under section 14302 of title 46 or, for vessels not measured under that section, as measured under section 14502 of 33 U.S.C.;
2. Is not a tank vessel;
3. Carries oil of any kind as fuel for main propulsion; and
4. Operates on the navigable waters of the United States, as defined in section 2101(1?a) of that title.

Norman Pins: Steel pins mounted along the aft bulwarks of a ship that limit the forward sweep of the tow wire.

Novel Life Saving Appliance or Arrangement: A lifesaving appliance or arrangement that has new features not fully covered by the provisions of this part but that provides an equal or higher standard of safety.

Ocean: Under this designation shall be included all tank vessels normally navigating the waters of any ocean or the Gulf of Mexico more than 20 nautical miles offshore.

Ocean Towing: Point-to-point towing outside of protected harbors.

Ocean Tugs: Ocean-going vessels designed specifically for towing.

Oceanographic Research Vessel: A vessel that the Secretary finds is being employed only in instruction in oceanography or limnology, or both, or only in oceanographic or limnological research, including studies about the sea such as seismic, gravity meter, and magnetic exploration and other marine geophysical or geological surveys, atmospheric research, and biological research.

Oceanographic Supply Vessel: A motor vessel that regularly carries goods, supplies, individuals in addition to the crew, or equipment in support of exploration, exploitation, or production of offshore mineral or energy resources.

Oceans: Means the waters seaward of the Boundary Lines as described in 46 CFR part 7. For the purposes of establishing sea service credit, the waters of the Inside Passage between Puget Sound and Cape Spencer, Alaska, and the inland waters of another country are not considered oceans.

OCIMF: Oil Companies International Marine Forum.

Officer Endorsement: An annotation on an MMC that allows a mariner to serve in the capacities listed in §10.109 of 46 CFR.

Officer in Charge of a Navigational Watch (OICNW): A deck officer qualified at the operational level. 

Officer in Charge of an Engineering Watch in a Manned Engine Room or Designated Duty Engineer in a Periodically Unmanned Engine Room (OICEW): An engineering officer qualified at the operational level. 

Officer in Charge, Marine Inspection, or OCMI: Means, for the purposes of 46 CFR subchapter B, the commanding officer of the National Maritime Center, or any

person designated as such by the Commandant, in accordance with 46 CFR §1.0l-5(b).

Offset Plate Shackle: A device used to connect towing components of different sizes

Offshore Facility: Means any facility of any kind located in, on, or under, any of the navigable waters of the United States, and any facility of any kind that is subject to the jurisdiction of the United States and is located in, on, or under any other waters, other than a vessel or a public vessel.

Offshore Installation Manager or OIM: Means an officer restricted to service on MODUs. An assigned offshore installation manager is equivalent to a master on a conventional vessel and is the person designated by the owner or operator to be in complete and ultimate command of the unit.

Offshore Supply Vessel: A motor vessel that regularly carries goods, supplies, individuals in addition to the crew, or equipment in support of exploration, exploitation, or production of offshore mineral or energy resources.

Oil: Means oil of any kind or in any form, including, but not limited to, petroleum, fuel oil, sludge, oil refuse, and oil mixed with wastes other than dredged spoil.

Oil Fuel: Oil used as fuel for machinery in the vessel in which it is carried.

Oil Fuel Unit: The equipment used for the preparation of oil fuel for delivery to an oil fired boiler, the equipment used for the preparation of heated oil fuel for delivery to an internal combustion engine, and any oil fuel pressure pump, filter, and heater that deals with oil at a pressure of more than 1.8 kilograms per square centimeter (25 p.s.i.) gauge.

Oil Spill Response Vessel: A vessel that is designated in its certificate of inspection as such a vessel, or that is adapted to respond to a discharge of oil or a hazardous material.

Oil Tanker: A tank vessel that is certificated to carry or carries oil in bulk as cargo or cargo residue. For the purposes of qualifying for an STCW endorsement for advanced oil tanker cargo operations, this includes tank barges.

On Location: Means that a mobile offshore drilling unit is bottom bearing or moored with anchors placed in the drilling configuration.

On the Brake: Towing with the tow hawser restrained by the brake system of the towing machine or winch.

On the Dog: Towing with the winch having a pawl engaged in the ratchet cog of the towing machine’s drum. Operative/emergency use of a winch dog restricts the ability to release a tow wire unless the machine is equipped with a remote release mechanism.

On-Board Communication Station: A low-powered mobile station in the maritime mobile service intended for use for internal communications on board a ship, or between a ship and its lifeboats and life-rafts during lifeboat drills or operations, or for communication within a group of vessels being towed or pushed, as well as for line handling and mooring instructions.

Onshore Facility: Means any facility (including, but not limited to, motor vehicles and rolling stock) of any kind located in, on, or under, any land within the United States other than submerged land.

Open Throat Spelter Socket: A wire rope termination that is shaped similarly to a shackle; socket mates with a closed socket.

Operate, Operating, or Operation (as applied to the manning requirements of vessels carrying

passengers): Refers to a vessel any time passengers are embarked whether the vessel is underway, at anchor, made fast to shore, or aground.

Operating Station: The principal steering station on the vessel, from which the vessel is normally navigated.

1. Operational Level: Means the level of responsibility associated with:
2. Serving as officer in charge of a navigational or engineering watch, or as designated duty engineer for periodically unmanned machinery spaces, or as radio operator onboard a seagoing ship; and
3. Maintaining direct control over the performance of all functions within the designated area of responsibility in accordance with proper procedures and under the direction of an individual serving in the management level for that area of responsibility.

Operator: Means any person including, but not limited to, an owner, a charterer, or another contractor who conducts, or is responsible for the operation of a vessel.

Orally Assisted Examination: An examination as described in 46 CFR, part 11, subpart I of subchapter B administered orally and documented by a Coast Guard examiner.

Otherwise Subject to the Jurisdiction of the United States: Means subject to the jurisdiction of the United States by virtue of United States citizenship, United States vessel documentation or States numbering, or as provided for by international agreement to which the United States is a party.

Overall lo Length: Means-

1. For a foreign vessel or a vessel engaged on a foreign voyage, the greater of:
2. 96 percent of the length on a waterline at 85 percent of the least molded depth measured from the top of the keel (or on a vessel designed with a rake of keel, on a waterline parallel to the designed waterline); or
3. The length from the fore side of the stem to the axis of the rudder stock on that waterline; and
4. For any other vessel, the horizontal distance of the huJl between the foremost part of the stem and the aftermost part of the stern, excluding fittings and attachments.

Overall Length: The horizontal distance of the hull between the foremost part of the stem and the aftermost part of the stem, excluding fittings and attachments.

Overriding Operational Condition: Means circumstances in which essential shipboard work cannot be delayed due to safety or environmental reasons, or could not have reasonably been anticipated at the commencement of the voyage.

Owner or Operator: Means-

1. In the case of a vessel, any person owning, operating, or chartering by demise, such vessel, and
2. In the case of an onshore facility, and an offshore facility, any person owning or operating such onshore facility or offshore facility, and
3. In the case of any abandoned offshore facility, the person who owned or operated such facility immediately prior to such abandonment.

Padeye: A metal fitting welded to a deck or bulkhead designed to accept a chain or shackle.

Panama  Type Fairlead or Chock: A non-roller type fairlead mounted at the ship’s side and enclosed so that mooring lines may be led to shore with equal facility either above or below the horizontal. Strictly pertains only to fairleads complying with the Panama Canal Regulations, but often applied to any closed fairlead or chock.

Parceling: Wrapping a line or wire with strips of canvas.

Partially Protected Waters: Means- 

1. Waters within 20 nautical miles (37 kilometers) of the mouth of a harbor of safe refuge, unless determined by the OCMI to be exposed waters; and
2. Those portions of rivers, harbors, lakes, etc. which the OCMI determines not to be sheltered.

Participation: When used with regard to the service on transfers required for tankerman by §13.120, §13.203, or §13.303 of 46 CFR subchapter B, means either actual participation in the transfers or close observation of how the transfers are conducted and supervised.

Passenger: Means an individual carried on the vessel except:

1. The owner or an individual representative of the owner or, in the case of a vessel under charter, an individual charterer or individual representative of the charterer;
2. The master; or
3. A member of the crew engaged in the business of the vessel who has not contributed consideration for carriage and who is paid for on board services.

Passenger For Hire:  A passenger for whom consideration is contributed as a condition of carriage on the vessel, whether directly or indirectly flowing to the owner, charterer, operator, agent, or any other person having an interest in the vessel.

Passenger Ship Safety Certificate: A certificate issued by the Commandant of the Coast Guard after inspection of a passenger ship, which complies with the requirements of the Safety Convention.

Passenger Vessel: Means-

1. On an international voyage, a vessel of at least 100 tons gross tonnage carrying more than 12 passengers; and
2. On other than an international voyage, a vessel of at least 100 tons gross tonnage:
3. Carrying more than 12 passengers, including at least one passenger-for-hire; or
4. That is chartered and carrying more than 12 passengers; or
5. That is a submersible vessel carrying at least one passenger­ for-hire.

Passes a Chemical Test for Dangerous Drugs: Means that the result of a chemical test conducted according to 49 CFR part 40 is reported as “negative” by a Medical Review

Officer according to that part.

Passport: Any travel document issued by competent authority showing the bearer’s origin, identity, and nationality, if any, which is valid for the admission of the bearer into a foreign country.

Pawl: A device that engages cogs in a wheel allowing rotation in only one direction.

Pay Out: To slack off on a line, or let it run out.

Pear-Shaped Detachable Links: A detachable link used to connect a small fitting or chain to a larger fitting or chain.

Pedestal Roller Fairlead: A roller fairlead usually carrying a mooring in a horizontal plane. Its purpose is to change the direction of lead of a mooring or other line on a ship’s deck.

Pelican Hook: A hook that can be opened while under strain by knocking away a locking ring that holds it closed; used to provide an instantaneous release.

Pendant (Pendant Rig): A single wire or chain that leads from the apex of a towing bridle to the towline; a single wire or chain that leads from the bow of the tow to connect to the tow hawser; a length of wire used as an underrider wire in a “Christmas tree” rig.

Periodically Unattended Engine Room: Means a space containing main propulsion and associated machinery and all sources of main electrical supply which is not at all times manned under all operating conditions, including maneuvering.

Permeability: The percentage of the volume of a space that can be occupied by water.

Permit: Refers to endorsement on the certificate of inspection, authorizing the presence on board of liquid flammable or combustible cargoes in bulk, issued by an Officer in Charge, Marine Inspection, for a tank vessel, which is found to be in substantial compliance with the regulations in 46 CFR § 30.10-49.

Person: Includes an individual, firm, corporation, association , and a Partnership. 

Persons in Addition to Crewmember:  Mean any person onboard the vessel, including passengers; who are not included on the list of crewmembers.

Pilot: Means a Federal pilot required by 46 U.S.C. 764, a state pilot required under the authority of 46 U.S.C. 211, or a registered pilot required by 46 U.S.C. 216.

Pilot Boarding Equipment and Point of Access: Pilot  boarding equipment means-

1. A pilot ladder, accommodation ladder, pilot hoist, or combination of them as required by this subchapter.
2. Point of access means the place on deck of a vessel where a person steps onto or off of pilot boarding equipment.

Pilot of Towing Vessels: A qualified officer of a towing vessel operated only on inland routes.

Pilotage Waters: The navigable waters of the United States, including all inland waters and offshore waters to a distance of three nautical miles from the baseline from which the Territorial Sea is measured.

Pitch: Fore-and-aft angular motion of a ship’s bow or stem in a seaway about the athwartships axis. See also “sway” and “yaw.”

Plate Shackle: A connecting device made up of two metal plates and bolts, used to connect the towing pendant and the towline, or to serve as a connecting unit in other parts of a towing rig.

Point-to-Point Towing: Towing a vessel from one harbor to another.

Popped Core: The phenomenon of wires flaring out on one side of a wire rope, exposing the core of the wire. This can occur when there is a sudden release of a heavy load on a wire rope.

Port: The left-hand side of a ship when looking forward; the opposite of “starboard.”

Port Operations Communications: Communications in or near a port, in locks or in waterways between coast stations and ship stations or between ship stations, which relate to the operational handling, movement and safety of ships and in emergency to the safety of persons.

Port or Place of Departure: Any port or place in which a vessel is anchored or moored. 

Port or Place of Destination: Any port or place in which a vessel is bound to anchor or moor.

Portable Ship Station: A ship station, which includes a single transmitter, intended for use upon two or more ships.

Position Report (PR): A vessel must report its name and position:

1. Upon point of entry into a VMRS area;
2. At designated reporting points as set forth in 33 CFR §161.20 subpart C; or
3. When directed by the Center.

Poured Socket: A wire rope termination installed by pouring molten zinc over splayed wire, often referred to as “spelter socket.”

Power Block (Transport Block): A portable, hydraulic motor-driven line sheave, providing back tension to the traction winch.

Practical Demonstration: Means the performance of an activity under the direct observation of a designated examiner or qualified assessor for the purpose of establishing that the performer is sufficiently proficient in a practical skill to meet a specified standard of competence or other objective criterion.

Precautionary Area: A routing measure comprising an area within defined limits where vessels must navigate with particular caution and within which the direction of traffic may be recommended.

Pressure Vacuum Relief Valve: Any device or assembly of a mechanical, liquid, weight, or other type used for the automatic regulation of pressure or vacuum in enclosed places.

Preventer: Any line, wire, or chain whose general purpose is to act as a safeguard in case something else carries away.

Priority Access: Treatment given by communications systems to place distress and ship security alerts and calls ahead of all other traffic.

Private Coast Station: A coast station, not open to public correspondence, which serves the operational, maritime control and business needs of ships.

Product Carrier: A tanker engaged in the trade of carrying oil except crude oil.

Proficiency: Means having the practical ability to apply the necessary knowledge, skill, and experience.

Prohibited Weapon: A firearm, knife, or other device or substance that is not permitted on board a vessel or the presence of which is regulated on board a vessel under policy established by the operator under their initiative or pursuant to state or local law.

Propulsion Power: The total maximum continuous-rated output power of the main propulsion machinery of a vessel determined by the manufacturer, in either kilowatts or horsepower, which appears on the ship’s Certificate of Registry or other official document and excludes thrusters and other auxiliary machinery.

Protected Waters: Sheltered waters presenting no special hazards such as most rivers, harbors, lakes, etc.

Public Coast Station: A coast station that offers radio communication common carrier services to ship radio stations.

Public Correspondence: Any telecommunication which the offices and stations must, by reason of their being at the disposal of the public, accept for transmission.

Public Vessel: A vessel that-

1. Is owned, or demise chartered, and operated by the United States Government or a government of a foreign country; and
2. Is not engaged in commercial service.

Push-Mode ITBs: Those ITBs that involve a rigid coupling system and, when not coupled to the barge, are incapable of conducting towing in any other configuration (such as astern or alongside) because, by themselves, they have very limited seakeeping capability. The propelling unit moves as one with the barge unit.

Qualified Assessor or QA: A person who is qualified to evaluate, for STCW endorsements, whether an applicant has demonstrated the necessary level of competence in the task for which the assessment is being made. The Coast Guard must individually approve this person.

Qualified Instructor: A person who has been trained in instructional techniques and is otherwise qualified to provide required training to candidates for an MMC endorsement. A faculty member employed at a State maritime academy or the U.S. Merchant Marine Academy operated under 46 CFR part 310 and instructing a course on merchant marine officer or rating knowledge, understanding, or proficiency requirements is qualified to serve as a qualified instructor in his or her area of specialization without individual evaluation by the Coast Guard.

Qualified Rating: Means various categories of able seaman, qualified member of the engine department, or tankerman endorsements issued on MMCs.

Quality Standard System or QSS:  A set of policies, procedures, processes, and data required to establish and fulfill the organization’s objectives.

Quarter: One side or the other of the stern of a ship.

Quarter Bitts: Single or double post bitts located on the vessels quarter.

Racking: Horizontal movement of the shackle, which tends to force the jaws of the shackle against the padeye plate causing the jaws to open.

Radar Beacon (RACON): A receiver-transmitter which, when triggered by a radar, automatically returns a distinctive signal which can appear on the display of the triggering radar, providing range, bearing and identification information.

Radioprinter Operations: Communication by means of a direct printing radiotelegraphy system using any alphanumeric code, within specified bandwidth limitations, which is authorized for use between private coast stations and their associated ship stations on vessels of less than 1600 gross tons.

Rail: An open fence or handrail aboard ship.

Raise of Grade: An increase in the level of authority and responsibility associated with an officer or rating endorsement, such as from mate to master or second assistant engineer to first assistant engineer.

Range: The layout of anchor chain in even rows.

Range Up:  To reduce the range between tow and tug, accompanied by the tendency for the tow to overtake the tug by sheering out to the side.

Rating Endorsement: Is an annotation on an MMC that allows a mariner to serve in those capacities set out in §10.109 of 46 CFR.

Reaching Pendant: Used between the tow and the towing hawser to ensure a safe stand off during hookup or disconnect (see also “leading pendant”).

Recessed Bitt(s): A bitt(s) recessed in the ship’s side shell.

Recognized Classification: Means the American Bureau of Shipping or other classification Society society recognized by the Commandant.

Reeving: The threading of a line or wire through a block, sheave, or other parts of a wire rope system.

Regional Examination: A field office of the National Maritime Center that receives Center or REC and screens credential applications, conducts approved course oversight, and administers Coast Guard examinations as required by 46 CFR §10.107 subchapter B.

Regulated Navigation Areas: A regulated navigation area is a water area within a defined boundary for which regulations for vessels navigating within the area have been established under this 33 CFR §165.10.

Regulatory Measurement System: A U.S. tonnage measurement system with a historical basis that requires that all closed-in spaces on a vessel be measured and treated according to their use. Gross tonnages assigned under this system are referred to in terms of gross register tons (GRT). Prior to 1983, the regulatory measurement system was the only U.S. tonnage measurement system available.

Reid Vapor Pressure: The vapor pressure of a liquid at a temperature of 100 °F, expressed in pounds per square inch absolute, as determined by the Reid Method as described in the American Society for Testing Materials Standard D 323 (incorporated by reference, see 46 CFR §30.01-3), Method of Test for Vapor Pressure of Petroleum Products. This Standard is available at Headquarters for reading purposes or it may be purchased from the Society at 100 Barr Harbor Drive, West Conshohocken, PA 19428-2959.

Relative Drift: The difference in the rates and directions of motion of two vessels caused by their differing reactions to wind, sea, and current.

Remove or Removal: Refers to containment and removal of oil or hazardous substances from the water and shorelines or the taking of such other actions as may be necessary to prevent, minimize, or mitigate damage to the public health or welfare, including, but not limited to, fish, shellfish, wildlife, and public and private property, shorelines, and beaches.

Repair Lockers: Storage spaces within the ship, which contains damage control equipment or the repair and control of damage due to battle, flooding, or fire.

Rescue Boat: A boat designed to rescue persons in distress and to marshal survival craft.

Rescue Towing: Saving a stricken ship at sea, or towing a disabled ship from the scene of a successful salvage to a safe refuge.

Reserve Buoyancy: A measure of the capability of a ship to be flooded or ballasted without sinking.

Resistance: A force that retards, hinders, or opposes motion, or opposes motion.

Rest: A period of time during which the person concerned is off duty, is not performing work (which includes administrative tasks such as chart corrections or preparation of port-entry documents), and is allowed to sleep without interruption.

Restricted Area: Means spaces that are essential to the operation, control, or safety of the vessel.

Restricted Tankerman Endorsement: A valid tankerman endorsement on a Merchant Mariner Credential restricting its holder, as the Coast Guard deems appropriate. For instance, the endorsement may restrict the holder to one or a combination of the following:

1. A specific cargo or cargoes; a specific vessel or vessels;
2. A specific facility or facilities; a specific employer or employers;
3. A specific activity or activities (such as loading or unloading in a cargo transfer); or a particular area of water.

Retrieval: The safe recovery of survivors.

Retrieval Pendant: A wire rope leading from the deck of the tow to the end of the towing pendant or flounder plate to facilitate bringing the tow gear back onto the foredeck.

Rigging: (Jewelry)Gear used to fasten together system components.

Rivers: Means a river, canal, or other similar body of water designated as such by the Coast Guard.

Rockwell C: A measurement of material hardness.

Roll: Side-to-side angular motion of a ship about its longitudinal axis. See also “pitch,” “sway” and “yaw.” 

Roller Fairlead: A chock fitted with a roller.

Ro11 Period: A measurement of the time required for a ship to roll from starboard to port and back to starboard or vice versa.

Route: The general geographic body or bodies of water endorsed on the face of a license specifically, oceans, near-coastal, Great Lakes­ inland, western rivers, or limited local area.

Saddle: A device on the stem of the towing vessel against which the bow of the tow can be brought up hard and maintained in position during ice operations.

Safe and Suitable Person: A person whose prior record, including but not limited to criminal record and/or NDR record, provides no information indicating that his or her character and habits of life would support the belief that permitting such a person to serve under the MMC and/or endorsement sought would clearly be a threat to the safety and security of life or property, detrimental to good discipline, or adverse to the interests of the United States. See 46 CFR §10.211 and §10.213 for the regulations associated with this definition.

Safe Haven: An area that can provide shelter from the sea and the weather. 

Safe Working Load: The load for which a rope, fitting, or working gear is designed.

Safety Communication: The transmission or reception of distress, alarm, urgency, or safety signals, or any communication preceded by one of these signals, or any form of radio communication which, if delayed in transmission or reception, may adversely affect the safety of life or property.

Safety Factor: A multiple representing extra strength over maximum intended stress.

Safety Shackle: A connecting device similar to the common shackle except that the mortise is held closed by a nut and bolt.

Safety Signal: Means-

1. The safety signal is the international radiotelegraph or radiotelephone signal, which indicates that the station sending this signal is preparing to transmit a message concerning the safety of navigation or giving important meteorological warnings.
2. In radiotelegraphy, the international safety signals consist of three repetitions of the group “TIT,” sent before the can, with the letters of each group and the successive groups clearly separated from each other.
3. In radiotelephony, the international safety signal consists of three oral repetitions of “Security,” pronounced as the French word “Securite,” sent before the call.
4. For GMDSS, safety calls result in an audible alarm and visual indication that the station sending this signal has a very urgent message to transmit concerning the safety of navigation or giving important meteorological warnings.

Safety Track: A T-shaped track running the length of the submarine’s topside to which personnel safety lines can be attached.

Safety Zone: Is a water area, shore area, or water and shore area to which, for safety or environmental purposes, access is limited to authorized persons, vehicles, or vessels. It may be stationary and described by fixed limits or it may be described as a zone around a vessel in motion.

Sag (Sagging): Deviation of the keel from a straight line when the keel is concave downward. Also, the concave curve of a towline said to have catenary.

Sail: The part of a modem submarine extending above the main deck or hull, housing the periscope supports, various retractable masts, and the surface conning station or bridge.

Sail Area: The vertical hull surface of a ship on which the wind exerts force.

Sailing Plan (SP): Unless otherwise stated, at least 15 minutes before navigating a VTS area, a vessel must report the:

1. Vessel name and type;
2. Position;
3. Destination and ETA;
4. Intended route;
5. Time and point of entry; and
6. Dangerous cargo on board or in its tow, as defined in §160.203 of this chapter, and other required information as set out in §160.211 and §160.213 of33 CFR, if applicable.

Sailing Vessel: A vessel propelled only by sails.

Salvage Towing: Follows very closely after a salvage operation, such as fire fighting, flooding control, battle damage repair, or retraction from stranding.

Satellite System: The space segment, land earth station (or equivalent), and arrangements for controlling the space segment and the network control facilities governing access.

Scientific personnel: Individuals on board an oceanographic research vessel only to engage in scientific research, or to instruct or receive instruction in oceanography or limnology.

Scope: The amount of towline streamed. 

Screw: The propeller of a ship.

Screw-Pin Shackle: A type of shackle in which the pin passes through one side of the shackle and threads into the other side of it to form a closure.

Scuttle: Small, quick-closing access hole.

Sea Anchor: A device, usually made of wood and/or canvas, streamed by a vessel or boat in heavy weather in order to hold the bow or stern into the sea.

Seagoing: The operation of a ship seaward of the baseline from which the territorial sea is measured.

Seagoing Barge: Means-

1. All nonself-propelled vessels of 100 gross tons and over that proceed on voyages on the high seas or ocean are subject to inspection and certification as seagoing barges.
2. In applying the laws and regulations to manned seagoing barges, one criterion for invocation of safety standards is the description of seagoing barges by relative size in gross tons. When it is determined by the Commandant that the gross register tonnage for a particular manned seagoing barge, which is attained by exemptions, reductions, or other devices in the basic gross tonnage formulation, will circumvent or be incompatible with the application of specific safety requirements in the regulations in this subchapter for a manned seagoing barge of such physical size, the Commandant shall prescribe the regulations to be made applicable to such seagoing barge. When the Commandant determines that the gross register tonnage is not a valid criterion for the invocation of safety requirements based on relative size, the parties involved will be informed of the determination and of the regulations applicable to such manner seagoing barges, and before being permitted to operate such seagoing barges, compliance therewith shall be required. Endorsements or notations on the seagoing barge1s certificate of inspection may be made as appropriate. 

Seagoing Condition: Means the operating condition of the vessel with the personnel, equipment, fluids, and ballast necessary for safe operation on the waters where the vessel operates.

Seagoing Motor Vessel: A motor vessel of at least 300 gross tons as measured under section 14502 of 46 U.S.C, or an alternate tonnage measured under section 14302 of 46 U.S.C. as prescribed by the Secretary under section 14104 of 46 U.S.C. making voyages beyond the Boundary Line.

Seagoing Service: Means service onboard a ship/vessel relevant to the issue of a credential or other qualification.

Seagoing Vessel: A ship that operates beyond the boundary line specified in 46 CFR part 7.

Second Engineer Officer: An engineer officer next in rank to the chief engineer officer and upon whom the responsibility for the mechanical propulsion and the operation and maintenance of the mechanical and electrical installations of the ship will fall in the event of the incapacity of the chief engineer officer.

Secondary Towline: An emergency towline rigged on the tow prior to getting underway. It can be deployed rapidly without assistance from personnel on board the tow.

Secretary: Means the Secretary of the department in which the Coast Guard is operating.

Section Modulus: As used in reference to wire rope, the effective area of the steel in wire rope multiplied by the modulus of elasticity of the steel.

Security zones: Means-

1. A security zone is an area of land, water, or land and water which is so designated by the Captain of the Port or District Commander for such time as is necessary to prevent damage or injury to any vessel or waterfront facility, to safeguard ports, harbors, territories, or waters of the United States or to secure the observance of the rights and obligations of the United States.
2. The purpose of a security zone is to safeguard from destruction, loss, or injury from sabotage or other subversive acts, accidents, or other causes of a similar nature:
3. Vessels,
4. Harbors,
5. Ports, and
6. Waterfront facilities in the United States and all territory and water, continental or insular, that is subject to the jurisdiction of the United States.

Seize: To bind with small stuff, as one rope to another or a rope to a spar.

Selectable Transponder: A transponder whose coded response may be inhibited or displayed on a radar on demand by the operator of that radar.

Selective Calling: A means of calling in which signals are transmitted in accordance with a prearranged code to operate a particular automatic attention device at the station whose attention is sought.

Self Propelled: Has the same meaning as the terms “propelled by machinery” and “mechanically propelled.” This term includes vessels fitted with both sails and mechanical propulsion.

Self-Propelled Tank Vessel: A self-propelled tank vessel, other than a tankship. Self-Propelled Vessel: Any vessel with means of self-propulsion, including sails.

Senior Company Official: The president, vice president, vice president for personnel, personnel director, or similarly titled or responsible individual, or a lower-level employee designated in writing by one of these individuals for the purpose of certifying employment and whose signature is on file at the REC at which application is made.

Senior Company Official: The president, vice president, vice president for personnel, personnel director, or similarly titled or responsible individual, or another employee designated in writing by one of these individuals for the purpose of certifying employment.

Service (as used when computing the required service for endorsements): The time period, in days, a person is assigned to work. On MODUs, this excludes time spent ashore as part of crew rotation.

Service As: Used when computing the required service for MODU endorsements, means the time period, in days, a person is assigned to work on MODUs, excluding time spent ashore as part of crew rotation. A day is a minimum of four hours, and no additional credit is received for periods served over eight hours.

Service Spaces: Spaces that are used for galleys, pantries containing cooking appliances, lockers, storerooms, paint and lamp rooms and similar spaces that contain highly combustible materials, laundry, garbage and trash disposal and stowage rooms, workshops other than those forming part of the machinery spaces, and similar spaces and trunks to such spaces.

Serving: To wrap small stuff tightly around a rope that has been previously wormed and parceled.

Shackle: U-shaped metal fitting, closed at the open end with a pin, used to connect wire, chain, and similar components.

Shaft Horsepower: See “Horsepower, shaft.”

Shark Jaws: Mechanically operated stopper device located just forward of the towing or anchor handling vessel’s tow pins used to stopper off and hold, while under tension, towing pendants, chain and other equipment during tow connection or disconnection process or anchor handling operations.

Sheave: A pulley with a rim, used to support or guide a rope in operation.

Sheering: In towing, the tow’s meandering from the towing vessel’s track. The tow may sheer out to a constant position on one side of the tug’s track, or it may swing from one side to the other with a fairly long period of several minutes or more.

Ship: A vessel using any mode of propulsion, including sail and auxiliary sail.

Ship Earth Station: A mobile earth station in the maritime mobile-satellite service located on board ship.

Ship or Vessel Security: The person on board the vessel accountable to the master Officer for the security of the vessel, including implementation and maintenance of the Vessel Security Plan and for liaison with the Company Security Officer and the waterfront facility.

Ship Radio Station License: An authorization issued by the Commission to operate a radio station onboard a vessel.

Ship Security Alert System (SSAS) : Shipboard system required by SOLAS Regulation XI-2/ 6 to covertly send an alert to a competent authority of a vessel’s flag State indicating a security threat to the vessel.

Ship Security Plan: A plan required for ships subject to the provisions of the International Ship and Port Facility Security (ISPS) Code.

Ship Station: A mobile station in the maritime mobile service located on-board a vessel which is not permanently moored, other than a survival craft station.

Shock Line: A length of large diameter (12″-15″) nylon line generally 250 to 300 feet long used between a towing vessels tow wire and the tows towing bridle pendant or chain for the purpose of absorbing and dampening the shock on the tow gear by sea conditions.

Shoring: Process of placing props against structure or cargo to prevent braking, sagging, or movement in a seaway, or to hold ship upright in dry dock.

Short International Voyage: An international voyage in the course of which a vessel is not more than 200 miles from a port or place in which the passengers and crew could be placed in safety. Neither the distance between the last port of call in the country in which the voyage begins and the final port of destination, nor the return voyage, may exceed 600 miles. The final port of destination is the last port of call in the scheduled voyage at which the vessel commences its return voyage to the country in which the voyage began.

Short Stay: SA minimum distances between tug and tow used during harbor operations “to bring to short stay.”

Shot: A standard length of chain, 15 fathoms (90 feet).

Shut-off valve: A valve that closes a pipeline and provides nominal metal-to­ metal contact between the valve operating parts, including the disc and gate, and the valve body.

Side Bitt: Single or double bitts located approximately at the pivot point of a vessel

Side-Slipping: Moving sideways through the water.

Similar Stage of Construction: Means the stage at which:

1. Construction identifiable with a specific vessel begins; and
2. Assembly of that vessel has commenced comprising at least 50 metric tons (55.1 U.S. tons) or 1 percent of the estimated mass of all structural material, whichever is less.

Simulated Transfer: A transfer practiced in a course meeting the requirements of §13.121 of 46 CFR subchapter B that uses simulation to meet part of the service on transfers required for tankerman by §13.203 or §13.303 of subchapter B.

Skeg: A portion of the underwater hull with significant longitudinal and vertical dimensions but without appreciable transverse dimensions. Its purpose is to give directional stability to the hull. On some moveable twin skegged tows the skeg may be moved to increase directional stability and reduce yawing.

Slip: To part from an anchor by unshackling the chain. To release completely or let run overboard.

Slugged Welds: Slugged Welds involve laying welding rods, cables, bolts or other extraneous material in a welding groove and then welding over it.

Small Passenger Vessel: Means a vessel of less than 100 gross tons:

1. Carrying more than six passengers, including at least one passenger for hire;
2. That is chartered with the crew provided or specified by the owner or owner’s representative and carrying more than six passengers;
3. That is chartered with no crew provided or specified by the owner or owner’s representative and carrying more than 12 passengers; or
4. That is a submersible vessel carrying at least one passenger for hire.

Small Stuff: Any small-circumference line used for general purposes.

Smit Bracket: A fitting for securing the end link of a chafing chain consisting of two vertical plates mounted on a base with a sliding bolt passing through the plates. A fitting welded on deck to enable towing connections to be made quickly and securely; the bracket consists of a large sliding pin to receive the eye of a tow line; often found in pairs as a standard feature on some barges for connecting towing bridles; it was named after the inventor, Dutch towing specialist company, Smit International.

Snapback: The sudden recoil occurring when a line parts.

Snatch Block: A type of fairlead that can be opened easily to insert a bight of line.

Socket: A wire rope termination attached by spelter (zinc) or Thermo-set resin poured socket.

Sound: To measure the depth of water at sea or the depth of a liquid in a ship’s tanks. To strike a chain link with a hammer to detect cracks or loose studs.

Spark Arrester: Any device, assembly, or method of a mechanical, centrifugal, cooling, or other type and of a size suitable for the retention or quenching of sparks in exhaust pipes from internal combustion engines.

Special Division 0: A Class I, Zone 0 hazardous area in Article 505 of the National Electrical Code that may require special considerations for electrical equipment installed in such locations.

Special Personnel: All persons who are not passengers or members of the crew and who are carried on board a special purpose vessel in connection with the special purpose of that vessel or because of special work being carried out aboard that vessel. Special personnel include:

1. On oceanographic research vessels, scientific personnel; and
2. On nautical school vessels, students, cadets, and instructors who are not members of the crew.

Special Purpose Vessel: A mechanically self-propelled vessel, which by reason of its function carries on board more than 12 special personnel including passengers. Special purpose vessels include oceanographic research vessels and nautical school vessels.

Splay: To unplay and broom the bitter end of a wire rope, usually done preparatory to attaching a socket.

Spliced Eye: A wire rope termination formed by inlaying the rope and intertwining the strands to form an eye.

Spooling: Winding a rope on a reel or drum. 

Spring Lay Rope: A rope combining fiber and wire.

Spring Line: See “spring.”

Spring, Stretcher: A pendant or grommet used to dampen towline surges. Stability: Ability of a ship to right itself after being heeled over.

Staff Officer: A person who holds an MMC with an officer endorsement listed in §10.109(a)(36) through (a)(43) of this 46 CFR.

Standard of Competence: The level of proficiency to be achieved for the proper performance of duties onboard vessels according to national and international criteria.

Staple: A metal arch welded to a deck or cap rail and designed to fairlead lines.

Starboard: The right-hand side of a ship when looking forward; the opposite of “port.”

State: Means each of the several States of the United States, the District of Columbia, the Commonwealth of Puerto Rico, Guam, American Samoa, the United States Virgin Islands, the Trust Territories of the Pacific Islands, the Commonwealth of the Northern Marianas Islands, and any other commonwealth, territory, or possession of the United States.

Static Load: The force applied by deadweight, often referred to as the “average” or “mean” load.

Station: One or more transmitters or a combination of transmitters and receivers, including the accessory equipment, necessary at one location for carrying on radio communication services.

STCW: The International Convention on Standards of Training, Certification and Watchkeeping for Seafarers, J 978, as amended (incorporated by reference, see §10.103 of this subpart).

STCW Code: Means the Seafarers’ Training, Certification and Watchkeeping Code (incorporated by reference, see §10.103 of this 46 CFR).

STCW Endorsement: An annotation on an MMC that allows a mariner to serve in those capacities under §10.109(d) of 46 CFR. The STCW endorsement serves as evidence that a mariner has met the requirements of the STCW Convention.

Steady (or static) Towline Tension: Resistance of the ship to be towed, the tow hawser, and the vertical component of wire catenary.

Stem: The forward extremity of a ship’s hull. 

Stem: The rear section of a ship.

Stem Planes: The after horizontal control surfaces of submarine normally used to control depth and angles.

Stem Rollers: The horizontal and vertical rollers at the stem of a tug used to lead capture and control the tow hawser.

Steward’s Department: The department that includes entertainment personnel and all service personnel, including wait staff, housekeeping staff, and galley workers, as defined in the vessel security plan approved by the Secretary under 46 U.S.C. 70103(c). These personnel may also be referred to as members of the hotel department on a large passenger vessel.

Stokes Stretcher: A wire mesh container used to transfer injured personnel through hatches onboard ship.

Stopper: A short length of line wrapped around a line to stop it from running.

Strain: To draw or stretch tight; to injure or weaken by force, pressure, etc.; to stretch or force beyond the normal, customary limits; to change the form or size of, by applying external force.

Strap: A short working wire with a spliced eye at each end. Stream To extend or increase the scope of the tow hawser.

Strongback: A wood or metal bar, which is used to hold a patch or shoring in place.

Stud-Link: A chain link with a bar fitted across the middle to prevent the chain from kinking.

Submersible Pump: Watertight electric pump that can be lowered into a flooded compartment to pump it out.

Suction Lift: A measurement in feet of the ability of a pump to raise water or liquid to the intake of the pump that takes into account friction and entrance losses.

Suitcase drum: An auxiliary or second drum of a tug’s tow winch used for handling the work wire/ pendant wire in anchor handling operations. May also be used for tugs stem line, working wire/line during tow make-up and barge work and for storing under­ rider pendants.

Support Level: The level of responsibility associated with performing assigned tasks, duties, or responsibilities onboard a seagoing ship under the direction of an individual serving in the operational or management level.

Surge Gear: Lengths grade 2 or 3 stud link anchor chain (generally in one shot lengths) used between a towing vessels tow wire and the tows towing bridle pendant or chain for the purpose of absorbing and dampening the shock on the tow gear by sea conditions.

Survival Craft: A craft capable of sustaining the lives of persons in distress from the time of abandoning the vessel on which the persons were originally carried. The term includes lifeboats, life rafts, buoyant apparatus, and life floats, but does not include rescue boats.

Survival Craft Station: A mobile station in the maritime or aeronautical mobile service intended solely for survival purposes and located on any lifeboat, liferaft or other survival equipment.

Suspicious Vehicle: A vehicle that by the totality of the circumstances surrounding its appearance or actions, including but not limited to operation contrary to posted guidance and the experience and training of the observing official, presents a particularized and objective basis to suspect that it is engaged unusual or out of the ordinary behavior.

Swage: To connect, splice, or tenninate wire rope by use of steel fittings installed under extremely high pressure.

Sway: Motion of a ship in which it is displaced laterally, as distinct from rolling. See also “pitch,” “roll,” and ”yaw.”

Swede Wire: (Spring lay Wire) is a composite rope having three wire and three fiber strands laid alternately around a fiber core. It is generally used for pulling tow gear on board the tug and for hanging off tow gear on the tow. The construction is 6x3xl 9 6 strands alternating polypropylene and wire rope in each strand. The wire strands are 19 wires each and the poly is in the form of a single strand. The core of the entire rope is also polypropylene. Spring lay is used for the above named purposes because it is very flexible and even shock resistant but it is relatively weak at approximately 1/3 of regular wire rope strength.

Swing-Meter: An electronic or electric device that indicates the rate of tum of the vessel on board which it is installed.

Swivel: A removable anchor chain link fitted to revolve freely and thus keep turns out of a chain.

Synthetic Hawser: A line or pendant used for towing made from any of a group of continuous or synthetic fibers.

Tailboat: A tug positioned at the stem of a tow with a headline secured to the tow. It is used to assist the towing tug in controlling a tow that does not follow well or to provide the ability to slow or stop a tow as needed. 

Tandem (Tug or Tow): Units inline one unit in front of the other unit.

Tandem Tow: A tow of two vessels carried out by a tug having a double drum tow winch with two tow wires or by a tug with a single drum tow winch with an under-rider drum. A tug with a single drum tow winch can also tow multiple tows by utilizing intermediate hawsers between the tows.

Tank Barge: A non-self-propelled tank vessel.

Tank Room: The gastight space surrounding a natural gas fuel tank, containing all tank connections and all tank valves, which is designed to contain any leak of natural gas, including tank rooms configured as described in section 2.8.4.3 and 2.8.4.4 of IMO Resolution MSC.285 (86).

Tank Ship: A tank vessel propelled by mechanical means or sails.

Tank Vessel: A vessel that is constructed or adapted to carry, or that carries, oil or hazardous material in bulk as cargo or cargo residue, and that:

1. Is a vessel of the United States;
2. Operates on the navigable waters of the United States; or
3. Transfers oil or hazardous material in a port or place subject to the jurisdiction of the United States.

Tanker: A self-propelled tank vessel constructed or adapted primarily to carry oil or hazardous materials in bulk in the cargo spaces.

Tankerman: The terms for the ratings identify persons holding valid endorsements for service in the ratings issued under that part:

1. Tankerman-PIC.
2. Tankerrnan-PIC (Barge).
3. Restricted Tankerman-PIC.
4. Restricted Tank.erman-PIC (Barge).
5. Tankerman-Assistant.
6. Tankerman-Engineer.

Tankerman Assistant: A person holding a valid “Tankerman-Assistant” endorsement on his or her MMC. See 46 CFR, part 13, subpart D.

Tankerman Engineer: A person holding a valid “Tankerman-Engineer” endorsement on his or her MMC. See 46 CFR part 13, subpart E.

Tankerman PIC: A person holding a valid “Tankerman-PIC” endorsement on his or her MMC. See 46 CFR part 13, subpart B.

Tankerman PIC (Barge): A person holding a valid “Tankerman-PIC (Barge)” endorsement on his or her MMC. See 46 CFR part 13, subpart C.

Tankship: Any self-propelled tank vessel constructed or adapted primarily to carry oil or hazardous material in bulk as cargo or as cargo residue.

Termination: The fitting installed on the end of a wire rope or chain used in towing.

Texas Bar: A tow span style fitted with a donut and used primarily with tow wires.

Thimble: A grooved metal buffer fitted snugly into an eye splice.

Tiller (tiller arm): Casting or forging attached to the rudderstock.

Timberhead Bitts: Double post bitts located on barge comers to which lines or cables are secured.

Timber Packing: Large wooden planks used to reinforce hull plating.

Time charterer: The party who hires a vessel for a specific amount of time. The owner and his crew manage the vessel, but the charterer selects the ports of destination.

Tow Pins: Hydraulic, Pneumatic or manually controlled vertical rollers arranged at the stem in line with the tow winch(es) arranged to keep the tow wire running straight from the tow winch over the stem. Additionally tow pins serve as fairleads for bringing tow gear on board when making up tow.

Tow Point: The point on the tug where the towline exerts its force. This may be the winch, H-bitts, cap rail, Norman pins, or other points, depending on the towing configuration.

Tow Resistance: The total force resisting the movement of the tow.

Tow Spans: Transversely installed beams or pipe that bridge the caprails on the afterdeck of the tug.

Tow Strap: A short working line with a spliced eye at each end used for towing alongside.

Tow Winch: The tow winch is a rotating mechanical device with a horizontal shaft and spool(s)/drum(s) containing the towing vessel’s tow wire, powered by electricity, hydraulics, or internal combustion engines that forms the primary connection between towing vessel and the tow. It is located on the stem of the towing vessel right aft of the deckhouse and is used to stow, pay out or take in wire as needed

Tow(ing) Point: Point(s) of application of the tow line force to the tow. 

Towing Bracket: See “Smit towing bracket” or “tow pad.”

Towing Chock: Chock designed or dedicated to use during a towing operation.

Towing Command: The command that performs the tow.

Towing Hawser: Generally, the main towline that is carried by the tug or the principal segment of the towline.

Towing Hook: Heavy steel hooks mounted on vertical pins used to hold the eye of a tow hawser.

Towing Machine: A towing winch with automatic features to compensate for variations in towline tension.

Towing Officer’s Assesment Record (TOAR): A record used to document the training and assessment of a mariner in the towing industry.

Towing Pad: Large padeye to which a towline may be attached.

Towing Rig: Describes the entire system of components that make up the connection between the tug and the tow.

Towing Vessel: A commercial vessel engaged in or intending to engage in the service of pulling, pushing, or hauling alongside, or any combination of pulling, pushing, or hauling alongside.

Towing Vessel in Inland Service: A towing vessel that is not in ocean or coastal service.

Towing Vessel in Ocean or Coastal Service: A towing vessel that operates beyond the baseline of the U.S. territorial sea.

Towing Winch: A basic winch used in towing that stores, pays out, and heaves in the towing hawser to compensate for variations in towline tension.

Towline: See “towing hawser.”

Towline Fatigue: The weakening of a towline due to cyclic application of load. 

Towline Strength: The nominal breaking strength of the tow hawser.

Towline Tension: The stress imparted to a towline during a towing operation.

Toxic Vapor or Gas: A product for which emergency escape respiratory protection is required under Subchapter 17 of the International Code for the Construction and Equipment of Ships carrying Dangerous Chemicals in Bulle (IBC Code) and under Subchapter 19 of the International Code for the Construction and Equipment of Ships carrying Liquefied Gases in Bulk (IGC Code).

Traction Winch: A multi-sheaved device that generates line tension. Tension is generated by friction between the line and traction beads.

Training Program:  A combination of training, practical assessment, and service which provides an individual with all or part of the necessary knowledge, understanding, and proficiency required for a specific qualification.

Transfer: Any movement of fuel, dangerous liquid, or liquefied gas as cargo in bulk or as cargo residue to or from a vessel by means of pumping, gravitation, or displacement.

Transportation Worker Identification Credential (TWIC): An identification credential issued by the Transportation or Security Administration under 49 CFR part 1572.

Transverse: Lateral dimension or placement.

Tripping: When a frame or padeye experiences transverse loading, it may result in out of plane deformation such that it is no longer perpendicular to the deck or hull plating. It has the appearance of having “fallen over” and is said to be tripped. A structure in this condition has significantly reduced strength.

Tripping (also known as around by the tow, girting): A tug on a towline being overtaken and swung either being pulled alongside the tow or capsizing due to high athwartships tow line forces. “To trip on a tow” is also used to define the intended act of coming around on the tow after shortening the tow wire and coming alongside heads and tails to make up to the tow for alongside maneuvering or to release and hang off tow gear. 

Tucks: In splicing, the insertion of the end of a strand between the strands of a rope.

Turnbuckles: A metal device consisting of a threaded link bolt and a pair of opposite threaded screws capable of being tightened or loosened and used for setting up standing rigging or stoppers.

Two Valve Protection: Consists of either two valves wired shut or one valve and a blank flange.

Two-Blocking: Term describing when the two blocks of a block-and-tackle have been drawn together or tightened so that they touch.

U.S. Laws: Any law of the United States that uses gross or net tonnage as a parameter. This includes regulations addressing requirements for manning; licensing, navigation safety, and vessel inspection.

U.S. Tonnage Certificate:  U.S. Tonnage Certificate (formerly a Certificate of Admeasurement) is a document used to certify tonnages and registered dimensions assigned to a U.S. flag vessel. A U.S. Tonnage Certificate is required for vessels assigned tonnages under standard and dual measurement of the regulatory measurement system. It is highly recommended, though not required, that a copy of the U.S. Tonnage Certificate be carried on board the vessel at all times. Vessels measured under simplified measurement are not issued a U.S. Tonnage Certificate. For documented vessels, the simplified measurement tonnages are calculated by the Coast Guard and appear on the Certificate of Documentation.

Ultrasonic Inspection: A non-destructive testing method that uses high frequency sound waves to check for material thickness, laminations, and defects or inclusions.

Underrider: The wire rope, chain, or combination used as a pendant heavy enough to pass under a leading tow to a trailing tow at a sufficient depth not to foul on the leading tow.

Underway: Means that a vessel is not at anchor, made fast to the shore, or aground. When referring to a mobile offshore drilling unit (MODU), underway means that the MODU is not in an on­ location or laid-up status and includes that period of time when the MODU is deploying or recovering its mooring system.

Undocumented Vessel: Means a vessel not required to have a certificate of documentation issued under the laws of the United States.

Uninspected Passenger Vessel: An uninspected vessel:

1. Of at least 100 gross tons;
2. Carrying not more than I 2 passengers, including at least one passenger-for-hire; or
3. That is chartered with the crew provided or specified by the owner or the owner’s representative and carrying not more than 12 passengers; and
4. Of less than I 00 gross tons;
5. Carrying not more than six passengers, including at least one passenger-for-hire; or
6. That is chartered with the crew provided or specified by the owner or the owner’s representative and carrying not more than six passengers.

United States: The States, the District of Columbia, the Commonwealth of Puerto Rico, the Commonwealth of the Northern Mariana Islands, Guam, American Samoa, the Virgin Islands, and the Trust Territory of the Pacific Islands.

Unlawful Act: An act that is a felony under U.S. Federal law, under the laws of the states where the vessel is located, or under the laws of the country in which the vessel is registered.

Unlimited: An annotation on an MMC authorizing service on vessels of any tonnage or any propulsion power.

Upper Level: Used as a category of deck and engineer officer endorsements established for assessment of fees. Upper-level endorsements are those for which the requirements are listed in §11.404 to §11.407 of this subchapter and §11.510, §I 1.512, §t 1.514, and § I 1.516 of 46 CFR subchapter B.

Upper Wheel House: Raised wheelhouse above the wheelhouse with full bridge controls.

Urgency Signal: Means-

1. The urgency signal is the international radiotelegraph or radiotelephone signal, which indicates that the calling station has a very urgent message to transmit concerning the safety of a ship, aircraft, or other vehicle, or of some person on board or within sight.
2. In radiotelegraphy, the international urgency signal consists of three repetitions of the group “XXX,” sent before the call, with the letters of each group and the successive groups clearly separated from each other.
3. In radiotelephony, the international urgency signal consists of three oral repetitions of the group of words “PAN PAN”, each word of the group pronounced as the French word “PANNE” and sent before the call.
4. For GMDSS, urgency calls result in an audible alarm and visual indication that the station sending this signal has a very urgent message to transmit concerning the safety of a ship, aircraft, or other vehicle, or of some person on board or within sight.

Veer: Means-

1. Slacken or let out: to veer chain
2. Change direction or tum about or aside; shift, tum, or change from one course, position;
3. Change direction clockwise;
4. Alter the direction or course of tum;
5. Shift to a direction more nearly astern;
6. Change the course of a ship by turning the stem to the wind while advancing to windward, wear ship;
7. Tum (a vessel) away from the wind;
8. A change of direction, position, course, etc.; a sudden veer in a different direction.

Vehicle: Every type of conveyance capable of being used as a means of transportation on land.

Vertical Stem Rollers, Tow: Vertical rolling pins mounted on the caprail of a tug to restrain the tow hawser sweep.

Vessel: Every description of watercraft or other artificial contrivance used, or capable of being used, as a means of transportation on water other than a public vessel.

Vessel Constructed: A vessel, the keel of which is laid or which is at a similar stage of construction.

Vessel Movement Center (VMC): The shore-based facility that operates the vessel tracking system for a Vessel Movement Reporting System area or sector within such an area. The VMC does not necessarily have the capability or qualified personnel to interact with marine traffic, nor does it necessarily respond to traffic situations developing in the area, as does a Vessel Traffic Service (VTS).

Vessel Movement Reporting System (VMRS): A mandatory reporting system used to monitor and track vessel movements. This is accomplished by a vessel providing information under established procedures as set forth in this part in the areas defined in Table 161.12(c) of33 CFR (VTS and VMRS Centers, Call Signs/MMSI, Designated Frequencies, and Monitoring Areas).

Vessel Movement  or Reporting System (VMRS) User: A vessel, or an owner, operator, charterer, Master, person directing the movement of a vessel that is required to participate in a VMRS.

Vessel Personnel With Designated Security Duties:  A person, excluding the designated security officer (e.g., Company Security Officer (CSO), as defined in 33 CFR chapter

I, subchapter H, and Vessel Security Officer (VSO)), having specific security duties and responsibilities in accordance with the ship security plan.

Vessel Security Officer: A person onboard the vessel accountable to the Master and (VSO)designated by the Company as responsible for security of the vessel, including implementation and maintenance of the Vessel’s Security Plan, and for liaison with the Facility Security Officer and the vessel’s Company Security Officer.

Vessel Security Plan: A plan developed to ensure the application of measures on board the vessel designed to protect persons on board, the cargo, or the vessel from the risk of security incident.

Vessel Traffic Center (VTC): The shore-based facility that operates the vessel traffic service for the Vessel Traffic Service area or sector within such an area.

Vessel Traffic Service Area or VTS Area: The geographical area encompassing a specific VTS area of service as described in part 161 of 33 CFR. This area of service may be subdivided into sectors for the purpose of allocating responsibility to individual Vessel Traffic Centers or to identify different operating requirements. NOTE: Although regulatory jurisdiction is limited to the navigable waters of the United States, certain vessels will be encouraged or may be required, as a condition of port entry, to report beyond this area to facilitate traffic management within the VTS area.

Vessel Traffic Services (VTS): A service implemented under part 161 of 33 CFR by the United States Coast Guard designed to improve the safety and efficiency of vessel traffic and to protect the environment. The VTS has the capability to interact with marine traffic and respond to traffic situations developing in the VTS area.

Vessel/Waterfront Facility  Interface: The activities that occur when a vessel is directly and immediately affected by an action involving the movement of people, goods or the provisions of port services to or from the vessel.

Voith-Schneider Propeller: A propeller that generates thrust at right angles to the axis of

rotation, which, through control of the angle of attack of the vertical propeller blades, can be directed through 360 degrees thus acting as both propeller and rudder.

Voyage Charterer: The party who hires a vessel for a single voyage. The owner and his crew manage the vessel, but the charterer selects the ports of destination.

VTS Special Area: A waterway within a VTS area in which special operating requirements apply.

VTS User: A vessel, or an owner, operator, charterer, master, or person directing the movement of a vessel, that is:

1. Subject to the Vessel Bridge-to-Bridge Radiotelephone Act; or
2. Required to participate in a VMRS within a VTS area (VMRS User).

VTS User’s Manual: The manual established and distributed by the VTS to provide the mariner with a description of the services offered and rules in force for that VTS. Additionally, the manual may include chartlets showing the area and sector boundaries, general navigational information about the area, and procedures, radio frequencies, reporting provisions and other information, which may assist the mariner while in the VTS area.

Wa1lis Brake: A wire brake used for keeping a steady load on a wire rope as it is installed on a drum.

Warm Water: Water where the monthly mean low water temperature is normally more than 15 °C (59 °F).

Warping Head: The horizontal drum of a winch, around which a rope is wound for heaving in or paying out.

Warping Tug: A small boat used to control the heading and speed of a tow during connection of the towline.

Watch: The act of listening on a designated frequency.

Water Brake: A device attached to the stem of a vessel (usually in lieu of a propeller) that provides drag for directional stability.

Weather Deck: The uppermost deck exposed to the weather.

 Western Rivers: Means-

1. The Mississippi River;
2. The Mississippi River’s tributaries, South Pass, and Southwest Pass, to the navigational demarcation lines dividing the high seas from harbors, rivers, and other inland waters of the United States;
3. The Port Allen-Morgan City Alternate Route;
4. That part of the Atchafalaya River above its junction with the Port Allen-Morgan City Alternate Route including the Old River and the Red River; and
5. Those waters specified in 33 CFR 89.25.

Wetted Surface: The area of the vessel below the waterline,  which is exposed to the sea.

Wheel House: Main location of steering/engine controls and navigation equipment.

Whiskey Locker: Storage area below the wheelhouse.

Williams Target Sled: The target used most for gunnery exercises.

Winch: An electric, hydraulic, or steam machine aboard ship used for hauling in lines, wire, or chain.

Windward: Toward the wind.

Wire Rope: Rope constructed of wire strands twisted together, as distinct from the more common, and weaker, fiber rope.

Wire Rope Pendant: A length of wire with a termination fitting at each end.

Work Space: Any area on the vessel where the crew could be present while on duty and performing their assigned tasks.

Worst Case Discharge: Means-

1. In the case of a vessel, a discharge in adverse weather conditions of its entire cargo; and
2. In the case of an offshore facility or onshore facility, the largest foreseeable discharge in adverse weather conditions.

Y-Gate: A piping connection with a large inlet section and two smaller outlet sections to permit hookup of two hoses to one pump outlet.

Yawing: Failure of a vessel to hold a steady course because of forces of wind, sea, damage to vessel, etc. In towing, yaw angle is the difference between the tow’s heading and the tug’s heading. Yawing can be manifested by an oscillation of the tow’s heading by a small angle to either side of the base course, with the tow remaining on the same track as the tug. See also “sheer,” “sway,” “pitch,” and “roll.”

Yield Strength: A measure of the maximum stress that can be applied to a material without permanent deformation. This is the value of the stress at the elastic limit for materials for which there is an elastic limit.

Z-Drive Propulsion: A mode of propulsion that uses a 360 degree rotating drive which can be positioned in the hull during design to provide the optimum propulsion.

Conclusion on Subchapter M

If you’re running or maintaining towing vessels, you already know this isn’t an industry where details can slip. A missed inspection deadline, a poorly worded log entry, or an outdated understanding of what counts as a “designated examiner” can mean fines, delays, or worse.

With Subchapter M, the Coast Guard gave us more than just regulations. They gave us a shared vocabulary to talk about safety, equipment, and operations—regardless of where your vessels are based or how often you perform occasional towing.

So use this glossary. Reference it. Share it with your crew. Build it into your safety management system TSMS. Because understanding the language isn’t just about passing a coast guard inspection—it’s about protecting your people, your job, and your ability to operate

Frequently Asked Questions