A Merchant Mariner Credential (MMC) is a certification issued by the U.S. Coast Guard that qualifies individuals to work aboard commercial vessels. It serves as an official identification and ensures that mariners meet necessary training, medical, and security requirements. Jobs with an MMC can include deckhands, engineers, captains, and other maritime roles on cargo ships, ferries, tugboats, and other vessels. The type of work depends on the endorsements a mariner holds, such as Able Seaman or Qualified Member of the Engine Department (QMED). To obtain an MMC, applicants must complete training, pass a medical exam, and undergo a background check.