Common USCG Definitions and Acronyms

If you're new to the maritime industry, or interested in learning more, you've seen plenty of acronyms, numbers, and words that you're unfamiliar with.

We've created this page to help you understand what you're reading and help you on your journey.

Common Maritime Acronyms

AB - Able SeamanABW - Able Seaman Watch standerCFR - Code of Federal Regulations

CMTS - U.S. Committee on the Marine Transportation System

CoE - Center of Excellence for Domestic Maritime Workforce Training and Education; (plural: CoEs)

COTP - Captain of the Port

DHS - U.S. Department of Homeland Security

DoD - U.S. Department of Defense

DOL - U.S. Department of Labor

DOT - U.S. Department of Transportation

GRT - Gross Register Tons

IMO - International Maritime Organization

MARAD - Maritime Administration

MMC - Merchant Mariner Credential (issued by the U.S. Coast Guard)

MTC - Maritime training center

NMC - National Maritime Center (of the U.S. Coast Guard)

OICEW - Officer-in-Charge of an Engineering Watch

OICNW - Officer-in-Charge of a Navigational Watch

OUPV - Operator of Uninspected Passenger Vessels license

QMED - Qualified Member of the Engine Department REC - USCG Regional Exam Center

RFPEW - Rating Forming Part of an Engineering Watch

RFPNW - Rating Forming Part of a Navigational Watch ROTR - Rules of the Road

STCW - Standards of Training, Certification and Watchkeeping for Seafarers

TWIC - Transport Worker Identification Credential

TS - Training ship

TSA - Transportation Security Administration

USC - United States Code

USCG - U.S. Coast Guard

USMMA - U.S. Merchant Marine Academy

USN - U.S. Navy

Common Comparisons

Merchant Marine Credential (MMC) vs. U.S. Coast Guard (USCG) License

The phrase USCG License is considered a legacy term, but it’s still common within the maritime community. The USCG issues the MMC in accordance with Federal regulations. Each MMC describes the type of vessels, tonnage, horsepower, and waters/routes that the mariner is qualified for. For service in international waters, the MMC includes the appropriate endorsements according to the International Convention on Standards of Training, Certification and Watchkeeping for Seafarers (STCW).

The MMC replaced several other documents, including the Merchant Mariner's Document, merchant mariner license, Certificate of Registry, and separate STCW Certificates.

Inland vs. Near Coastal vs. Oceans vs. International Waters

These boundaries are established through international treaties and are described in 33 CFR.

33 CFR, Part 80 establishes the demarcation lines that delineate those waters upon which mariners shall comply with the International Regulations for Preventing Collisions at Sea, 1972 (72 COLREGS) and those waters upon which mariners shall comply with the Inland Navigation Rules.

The waters inside of the lines are Inland Rules waters. The waters outside the lines are COLREGS waters. COLREGS waters are further divided into near-coastal waters (ocean waters within 200 miles offshore from the U.S. and its possessions) and oceans (i.e., international waters) (46 CFR 10.107).

Ratings vs. unlicensed

Ratings is the internationally accepted term for merchant mariners who serve in positions other than shipboard officers. It’s also the term used within the U.S. Code and the Code of Federal Regulations. Since these individuals hold credentials other than a USCG license, they’re often referred to as unlicensed personnel.

Sea time vs. sea service

These terms are interchangeable and identify a day of service aboard a training ship or commercial vessel that’s credited towards fulfilling a credentialing requirement.

Ship vs. vessel

These terms are interchangeable.

Limited license vs. Unlimited license

Limited and unlimited are used to define different mariner credentials.

Limited licenses are credentials that include any limitations on vessel type, tonnage, horsepower (e.g., limited to smaller tugboats, offshore supply vessels, or fishing vessels), or restrictions on routes.

Unlimited licenses are credentials that allow mariners to serve on vessels without restrictions on vessel tonnage (for deck officers), vessel horsepower (for engineering officers), or routes (e.g., inland, near coastal, or oceans).

Terms and definitions

Able Seaman (AB)

(Able Seaman) is the generic term for the rating that allows the mariner to work in an unlicensed position on a vessel.The endorsement requires training and/or examination. The Able Seaman is a national credential issued to qualified deck personnel. The AB is not an officer. The STCW AB, is Able-Seafarer Deck.

Able Seaman - Unlimited

A mariner holding an AB Unlimited can serve on any vessel in the United States as an Able Seaman. To qualify a mariner needs to have three years service (1080 days) on deck of vessels operating on the ocean, near coastal waters or the Great Lakes.

Able Seaman - Limited

A mariner holding an AB Limited can serve in any Able Seaman capacity that is needed based on a vessel's Certificate of Inspection except where an AB - Unlimited is required in the safe manning document for that voyage. A mariner needs to have eighteen months of service (540 days) on deck of vessels of 100 gross tons or more which operate on the oceans, near coastal waters, Great Lakes, or navigable waters of the United States to qualify for an AB Limited.

Able Seaman - Special

A mariner holding an AB Special can serve in any Able Seaman capacity that is needed based on a vessel's Certificate of Inspection except where an AB - Unlimited or AB - Limited is required in the safe manning document for that voyage. A mariner needs to have twelve months of service (360 days) on deck of vessels which operate on the oceans, near coastal waters, Great Lakes, or navigable waters of the United States to qualify for an AB Special.

Able Seaman - OSV

A mariner holding an AB OSV can only serve on OSVs as an Able Seaman. The US Code which specifies AB OSV, 46 U.S.C. 7310, explains that Offshore Supply Vessels must be less than 500 gross tons and support exploration, exploitation or production of offshore mineral or energy resources. This means that an Able Seaman-OSV may be employed aboard any such vessel, including an uninspected towing vessel, involved in this industry. The endorsement in not valid as an Able Seaman on any other types of vessels if they are not working in the specified industry. A mariner needs to have six months of service (180 days) on deck of vessels which operate on the oceans, near coastal waters, Great Lakes, or navigable waters of the United States to qualify for an AB OSV.

Able Seaman - Fishing Industry

An AB Fishing can only serve as an Able Seaman on fish processing vessels. The endorsement in not valid as an Able Seaman on any other types of vessels. A mariner needs to have six months of service (180 days) on deck of vessels which operate on the oceans, near coastal waters, Great Lakes, or navigable waters of the United States to qualify for an AB Fishing Industry.

Able Seaman - Sail

An AB Sail can only serve as an Able Seaman on sailing school vessels. The endorsement in not valid as an Able Seaman on any other types of vessels. A mariner needs to have six months of service (180 days) on sailing school vessels, oceanographic research vessels powered primarily by sail, or equivalent sailing vessels which operate on the oceans, near coastal waters, Great Lakes, or navigable waters of the United States to qualify for an AB Fishing Industry.

Assistant engineer

For domestic endorsements, an assistant engineer is a qualified officer in the engine department, other than the chief engineer.

Assistance towing

This means towing a disabled vessel for consideration.

Anchor Watch

A proper anchor watch includes following procedures to detect a dragging anchor. Whenever weather, tide, or current conditions are likely to cause the vessel's anchor to drag, action is taken to ensure the safety of the vessel, structures, and other vessels, such as being ready to veer chain, let go a second anchor, or get underway using the vessel's own propulsion or tug assistance.

Barge

A barge is a non-self-propelled vessel as defined in 46 USC 102.

Boatswain (Bosun)

A boatswain is the leading seaman and supervisor of the deck crew. They supervise the maintenance of deck gear. This isn’t a credential, but an assignment on each vessel.

Boundary line

The Boundary line marks the dividing point between internal and offshore waters for several legal and regulatory purposes, including load line regulations. Boundary Lines are also used in crediting inland/offshore sea service for mariner licensing. They’re specified in 46 CFR Part 7 and do not include the Great Lakes.

Chief Engineer

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

Chief Mate

The Chief Mate is the deck officer next in rank to the master. They assume command of the vessel in the event of the incapacity of the master.

Code of Federal Regulations (CFR)

CFR is the official annual compilation of all regulations and rules put into effect during the previous year by the agencies of the U.S. government, combined with all the previously issued rules and regulations that are still in effect.

Credential

Credential means any or all of the following: Merchant Mariner’s Document (MMD), License, STCW endorsement, Certificate of Registry, or Merchant Mariner Credential (MMC).

Sea Day

A sea day is every day you are away from the pier for over 4 hours in a 24 hour period.

Deck department

The deck department aboard a ship is responsible for navigation, cargo, command, and control functions.

Designated Duty Engineer (DDE)

The DDE is a qualified engineer, who may be the sole engineer on vessels less than 500 GT with a periodically manned engine room.

Designated Person Ashore (DPA)

The DPA is a person not on the vessel but with direct access to the highest level of a company’s management. As described in the International Ship Management Code, the responsibility and authority of the Designated Person includes monitoring the safety and pollution prevention of each ship, and ensuring that adequate resources and shore-based support is available.

Document of Continuity

The DOC’s sole purpose is to maintain an individual’s eligibility for renewal of an endorsement. If a mariner’s credential has expired and is running out of time on its six-year grace period, the mariner can apply for a Document of Continuity which allows them to renew the credential at a later time beyond the grace period.

Once the grace period has expired on a credential, the license is gone. The DOC allows it to be resuscitated.

Domestic voyage

This is a voyage from one United States port to another United States port, without entering waters under the jurisdiction of another country. This includes a “voyage to nowhere” that returns to the originating port.

Endorsement

An endorsement is a statement of a mariner’s qualifications, which can include the categories of officer, staff officer, ratings, and/or STCW appearing on a merchant mariner credential.

Engine department

The engine department aboard a ship is responsible for the main propulsion and auxiliary systems as well as other mechanical, electrical, hydraulic, and refrigeration systems, sometimes including deck machinery and cargo-handling equipment.

Entry-level mariner

Entry level mariners hold no rating other than ordinary seaman, wiper and steward’s department food handler (FH).

First Class Pilot

A First Class Pilot accompanies vessels while they enter or leave port to ensure safe navigation of entrance and departure.

Great Lakes (GL)

There are five Great Lakes in the U.S. Lake Superior, Michigan, Huron, Erie, and Ontario. For purposes of requiring merchant mariner credentials with rating endorsements, the connecting and tributary waters are not part of the Great Lakes.

Gross register tons (GRT)

GRT is a measurement of the gross tons of the vessel under 46 USC Chapter 145, Regulatory Measurement.

Gross Tonnage (GT)

GT is a volume measurement rather than a weight. GT means the gross tonnage measurement of the vessel under 46 USC Chapter 143, Convention Measurement.

Increase-in-scope

An increase in scope means additional authority is added to an existing credential. For example: increasing from Master 25 GRT to Master 50 GRT.

Inland

Inland waters are the navigable waters of the United States shoreward of the Boundary Lines as described in 46 CFR Part 7, excluding the Great Lakes and, for towing vessels, excluding the Western Rivers.

Inspected vessel

An Inspected Vessel is one inspected by the Coast Guard and that has been issued a Certificate of Inspection. Vessels require a USCG inspection when they’re carrying more than six paying passengers.

Lifeboatman

A lifeboatman is a mariner who is qualified to take charge of, lower, and operate survival craft and related survival equipment on a vessel.

Lifeboatman-Limited

Lifeboatman limited is 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.

Limited

Limited is an annotation on an MMC which limits the operational authority of an endorsement to a specified tonnage, portions of a route, means of propulsion, or particular equipment (such as life rafts).

Master

The Master is the person having command of a vessel. The USCG Masters license is the highest-level license that you can acquire.

Mate

The Mate is a qualified officer working in the deck department, other than the master.

Merchant Mariner Credential (MMC)

MMC is the credential issued by the Coast Guard under 46 CFR Part 10. It combines the individual merchant mariner’s document, license, and certificate of registry, as well as the STCW endorsement. The MMC is a single credential that serves as the mariner’s qualification document, identification, and certificate of service.

National Officer Endorsement (formerly Domestic Officer Endorsement)

National Officer is an annotation on an MMC that allows a mariner to serve in the capacities listed in 46 CFR 10.109(a). The officer endorsement serves as the license and/or certificate of registry pursuant to 46 USC Subtitle II Part E.

National Rating Endorsement (formerly Domestic Rating Endorsement)

National Rating Endorsement is an annotation on an MMC that allows a mariner to serve in those capacities set out in 46 CFR 10.109(b) and (c).The rating endorsement serves as the merchant mariner’s document pursuant to 46 USC Subtitle II Part E.

National Maritime Center (NMC)

NMC is the licensing authority for the United States Coast Guard, under the Department of Homeland Security. The NMC issues credentials to qualified mariners.

Near Coastal (NC)

Near Coastal waters are not more than 200 miles offshore from the US and its possessions, except on MMCs endorsed as Operator of Uninspected Passenger Vessels for which a Near Coastal credential is limited to waters not more than 100 miles offshore from the US and its possessions.

Oceans (O)

Oceans are the waters seaward of the Boundary Lines as described in 46 CFR Part 7.

Officer in Charge, Marine Inspection (OCMI)

The commanding officer of the National Maritime Center or any person designated as such by the Commandant, in accordance with 46 CFR 1.01-15(b).

Officer in charge of an engineering watch (OICEW)

The OICEW serves in a manned engine room or designated duty engineer in a periodically unmanned engine room. The OICEW is an engineering officer qualified at the operational level on a vessel to which STCW applies.

Officer in charge of a navigational watch (OICNW)

The OICNW is a deck officer qualified at the operational level on a vessel to which STCW applies.

Ordinary Seaman (OS)

Ordinary Seaman is the entry level in the deck department. Wiper is the equivalent in the engine department.

OUPV (Operator of Uninspected Passenger Vessel/Six-Pack)

The OUPV license allows mariners to captain smaller, uninspected vessels with up to six paying passengers—which is why the OUPV is often called the Six-Pack license.

PQEB (Professional Qualification Evaluation Branch)

This is the part of the process that checks certificates such as First Aid/CPR, Proof of Ownership, and Sea Service.

Qualified Member of the Engine Department (QMED)

QMED is a generic name for one of six rating that permits the holder to serve in a non-licensed capacity in the engine room. A qualified member of the engine department is any person who holds an engine department rating issued by the U.S.

Coast Guard that is below licensed officer and above wiper. The endorsement requires training and/or an examination. QMED is the engine equivalent of the AB.

QMED - Any Rating

A QMED Any Rating is authorized to serve in any capacity on vessels that require a Electrician/Refrigerating Engineer, Fireman/Watertender, Junior Engineer, Oiler or Pumpman/Machinist. An applicant for a QMED Any Rating rating must have a minimum of six months (180 days) of underway service in a rating at least equal to that of wiper.

They then must take a USCG approved course that specifically includes QMED Any Rating or take all five exams at the USCG REC for Electrician/Refrigerating Engineer, Fireman/Watertender, Junior Engineer, Oiler and Pumpman/Machinist.

QMED - Electrician/Refrigerating Engineer

A QMED Electrician/Refrigerating Engineer is authorized to serve in this capacity for safe manning only on vessels that require a QMED Electrician/Refrigerating Engineer. They are not authorized to serve in another capacity unless the vessel COI explicitly authorizes one rating to be substituted for another.

An applicant for a QMED Electrician/Refrigerating Engineer rating must have a minimum of six months (180 days) of underway service in a rating at least equal to that of wiper. They then must take a USCG approved course or exams at the USCG REC for QMED Electrician/Refrigerating Engineer.

QMED - Fireman/Watertender

A QMED Fireman/Watertender is authorized to serve in this capacity for safe manning only on vessels that require a QMED Fireman/Watertender. They are not authorized to serve in another capacity unless the vessel COI explicitly authorizes one rating to be substituted for another.

An applicant for a QMED Fireman/Watertender rating must have a minimum of six months (180 days) of underway service in a rating at least equal to that of wiper. They then must take a USCG approved course or exams at the USCG REC for QMED Fireman/Watertender.

QMED - Junior Engineer

A QMED Junior Engineer is authorized to serve in this capacity for safe manning only on vessels that require a QMED Junior Engineer. They are not authorized to serve in another capacity unless the vessel COI explicitly authorizes one rating to be substituted for another.

An applicant for a QMED Junior Engineer rating must have a minimum of six months (180 days) of underway service in a rating at least equal to that of wiper. TThey then must take a USCG approved course or exams at the USCG REC for QMED Junior Engineer.

QMED - Oiler

A QMED Oiler is authorized to serve in this capacity for safe manning only on vessels that require a QMED Oiler. They are not authorized to serve in another capacity unless the vessel COI explicitly authorizes one rating to be substituted for another.

An applicant for a QMED Oiler rating must have a minimum of six months (180 days) of underway service in a rating at least equal to that of wiper. They then must take a USCG approved course or exams at the USCG REC for QMED Oiler.

QMED - Pumpman/Machinist

A QMED Pumpman/Machinist is authorized to serve in this capacity for safe manning only on vessels that require a QMED Pumpman/Machinistr. They are not authorized to serve in another capacity unless the vessel COI explicitly authorizes one rating to be substituted for another.

An applicant for a QMED Pumpman/Machinist rating must have a minimum of six months (180 days) of underway service in a rating at least equal to that of wiper. They then must take a USCG approved course or exams at the USCG REC for QMED Pumpman/Machinist.

Qualified rating

Rating are various categories of able seaman, qualified member of the engine department (QMED), or tankerman endorsements issued on merchant mariner credentials.

Raise of grade (raise-in-grade, RIG)

Raise in grade is an increase in the level of authority and responsibility associated with an officer or rating endorsement. For example: upgrading your license from Mate to Master or from Second Assistant Engineer to First Assistant Engineer.

Rating endorsement

Rating endorsement is an annotation on a merchant mariner credential that allows a mariner to serve in those capacities detailed in 46 CFR 10.109. This includes ratings such as: Able Seaman, Ordinary Seaman, QMED, etc.

RECs (Regional Exam Centers)

Regional Exam Centers (REC) are where you submit USCG License applications and take your USCG exams if needed. It is important that you provide the Regional Exam Center with a complete application package to avoid delay.

ROTR (Rules of the Road)

Rules of the Road are officially called the Navigation Rules. They are regulations which aid mariners in safe navigation, just as driving laws aid vehicles in safe driving. Professional mariners must be proficient in the Rules of the Road but all mariners should know and understand the Rules. The Rules are legally binding and application of them makes the waterways safer for everyone.

Safety Review

Every application that requires a safety and suitability evaluation is completed by the Safety and Suitability Evaluation Branch. The Transportation Security Administration (TSA) is the primary source for conducting background investigations.

Seagoing service

This is service onboard a ship/vessel that’s relevant to the issue of a credential or other qualification.

Seagoing vessel

A seagoing vessel is a self-propelled vessel that operates beyond the boundary line specified in 46 CFR Part 7.

Service (used for calculating the required service for endorsements)

Service, or sea service means the time period, in days, a person is assigned to work.

Ship

A ship or vessel is a self-propelled vessel using any mode of propulsion, including sail and auxiliary sail.

STCW

STCW is the International Convention on Standards of Training, Certification and Watchkeeping for Seafarers,1978. The STCW is a treaty, most recently revised in 2010 with the inclusion of the “Manila Amendments.”

STCW endorsement

STCW is an endorsement on an MMC that allows a mariner to serve in those capacities under 46 CFR 10.109(d). The STCW endorsement shows that a mariner has met the requirements of the STCW Convention.

Tankship

A tankship is a self-propelled tank vessel constructed or adapted primarily to carry oil or hazardous material in bulk as cargo or as cargo residue.

Transportation Worker Identification Credential (TWIC)

The TWIC is an identification credential issued by the Transportation Security Administration under 49 CFR Part 1572.

Underway

Underway means that a vessel is not at anchor, at shore, or aground.

Undocumented vessel

An undocumented vessel is one that’s not required to have a certificate of documentation (COD) issued under the laws of the United States.

Uninspected passenger vessel (UPV)

Uninspected vessels aren’t inspected by the USCG and can carry up to six paying customers. Any more than that requires the vessel to be inspected. There are still general requirements for uninspected vessels.

Unlimited tonnage

When a vessel’s gross tonnage is greater than 1600 GRT.

Vessel Security Officer (VSO)

The VSO is a person onboard the vessel accountable to the Master, and designated by the Company. They’re responsible for the 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.

Western Rivers

Western Rivers means the Mississippi River, its 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, and the Port Allen-Morgan City Alternative Route, and that part of the Atchafalaya River above its junction with the Port Allen-Morgan City Alternative Route including the Old River and the Red River and those waters specified by 33 CFR 89.25 and 89.27, and such other, similar waters as are designated by the COTP.

Note: “Western Rivers” aren’t rivers in the West. For example, the Columbia River is a river in the West, but not a “Western River.” In fact, none of the defined “Western Rivers” are located in the Western half of the United States.

USCG NMC Forms

CG-719B

The CG-719B form is the application form for Merchant Mariner Credentials. This form is used to apply for an original MMC, and renewal, duplicate, raise of grade, or new endorsement on an MMC.

CG-719C

The CG-719C form is used to disclose previous convictions, such as DUI, DWI, and other convictions.

CG-719K

The CG-719K is the application for the required medical certificate.  

CG-719P

The CG-719P form is the USCG periodic drug testing form.

CG-719S

The CG-719S is the Small Vessel Sea Service Form. This form is used by the Coast Guard to document and track your days and experience.

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