The documents that determine who you are, where you can sail, and what you're legally allowed to do.
Working as a merchant mariner requires more than a single "license." U.S. mariners operate under a layered system of identity documents, Coast Guard credentials, medical approvals, and training requirements — each serving a distinct legal purpose.
If you are starting from zero, most mariners follow this sequence — not because it's arbitrary, but because the system is designed this way.
The Transportation Worker Identification Credential verifies your identity and security clearance.
Many U.S.-flag vessels sail internationally or require international travel for crew changes.
The Merchant Mariner Credential authorizes you to work aboard U.S.-flagged vessels.
The National Maritime Center (NMC) is part of the U.S. Coast Guard and administers the merchant mariner credentialing system.
When mariners talk about "the Coast Guard" in credentialing conversations, they are usually referring to the NMC.
National Maritime CenterThese documents are foundational. They are not licenses — but without them, nothing else happens.
A security and identity credential required to access ports and vessels.
Required before applying for an MMC.
An international travel document required for most international service and many domestic positions.
Strongly recommended for all mariners.
The central credential in the U.S. maritime system.
The MMC is the central credential in the U.S. maritime system.
The MMC is a container. Licenses, ratings, and endorsements live inside it.
Entry-level MMC endorsements require no sea time and are designed for mariners entering the industry for the first time.
Common entry-level endorsements include:
All mariners must hold a valid Coast Guard medical certificate certifying fitness for duty.
A company or employer physical does not replace Coast Guard medical certification.
Required Form: CG-719K
Medical Certificate FormsOne of the most common sources of confusion in maritime careers.
National credentials govern your domestic authority to work aboard U.S.-flagged vessels.
STCW is an international framework established by the IMO. Required for most international voyages.
A mariner may hold a national license and still be prohibited from sailing internationally without appropriate STCW endorsements.
At the foundation of STCW is Basic Safety Training. BST is required for international voyages, most deep-sea vessels, and many government/commercial operations.
STCW does not replace national licenses — it supplements them.
What's the difference?
Grants legal authority to perform a role aboard a vessel.
Issued by the U.S. Coast Guard
Expands or limits that authority.
Also issued by the Coast Guard
Issued by schools, unions, or employers. Supports licenses and endorsements.
Does not grant authority by itself
Training supports licenses. It does not replace them.
In addition to Coast Guard requirements, mariners may need:
These requirements are important — but they sit on top of Coast Guard credentials, not instead of them.
