Merchant Mariner Credential (MMC)The Merchant Mariner Credential (MMC) is a passport style book that contains a mariner's professional qualifications in the form of endorsements.

Merchant Mariner Credential (MMC)

The Merchant Mariner Credential (MMC) is a passport style book containing your professional credentials to work on US flagged merchant vessels. Any US owned vessel carrying cargo or passengers for pay, regardless of size, is considered a US merchant vessel. Accoringly, the operator, and sometimes the crew, must hold the appropriate MMC license.The US Coast Guard issues three types of MMC licenses, called endorsements, national officer, national rating, and STCW.

National Officer

An officer is the mariner who runs the ship or a department on the ship. Most small vessels have only one department, deck. While larger vessels may have several departments. For example, engine, staff, steward, and medical. Additionally, ships that operate more than 12-hours a day may have more than one officer in a department.

Deck Officers

The most well-known are the deck officers. They include OUPV, Master, and Mate. While the OUPV and Master are both captains, the mate is there to give the captain a break on those long days. Which License is for you: OUPV or Master >>

National Rating

As with officers, each department has ratings. With some exceptions, all seagoing vessels 100 GRT (about 65-feet) and larger must be crewed by sailors with MMC ratings. There are ratings for both engine and deck. Again, the most well know are the deck ratings. There are three basic deck ratings, Ordinary Seaman (OS), Able Body Seaman (AB), and Tankerman.

OS and AB

The OS is an entry level rating. While the AB is for the experienced mariner. Which Deck Rating: AB or OS >>


The highest paid of the deck ratings is tankerman. They are in charge of the transfer of dangerous liquid cargoes to and from the vessel. Therefore, they well paid. More about Tankerman and AB ratings >>


These are the international standards that apply to inspected seagoing vessels 200 GRT (500 GT) and larger. In other words, STCW does not apply to vessel less than 200 GRT, uninspected vessels of any size, or any size vessel that operates exclusively on inland waters. In the world of small vessels, STCW rarely applies.

Coast Guard form 719B, Small Vessel Sea Service identifies small vessels as less than 200 GRT. This form is used to document a mariner’s experience on small vessels.

Merchant Mariner Credential (MMC) Classes

ColPac Maritime provides USCG approved classes for MMC endorsements. Click here to view the full list of classes we offer >>