The Merchant Mariner Credential (MMC) is an official document issued by the U.S. Coast Guard that allows individuals to work on commercial vessels. It serves as proof of a mariner's qualifications, including their training, experience, and any endorsements for specific types of vessels or operations. To obtain an MMC, applicants must meet certain requirements, such as passing medical and background checks, and completing safety training courses. The credential is essential for those pursuing careers in the maritime industry, including roles on cargo ships, fishing vessels, and passenger ferries.