Mate of 200 or less GRT upon Great Lakes and Inland Waters. This is an advanced-level merchant mariner credential. The general requirements for this credential are TWIC Card (Identification, Fingerprints, Citizenship, Social Security number, etc), CG-719B Application, NDR Consent & Check, Oath, 3 letters of recommendation, photograph (supplied by TSA), SSEB Screening complete, age of 21 or over, CG-719K Physical Exam, Medical Tab in MMLD, Drug Testing Compliance, Mariner Fees, and Sea Service Letters or Discharges. Sea service requirements include recency- 90 days in the past 3 years on vessel. Great Lakes - 180 days of service in the deck department, of which 90 days must have been on Great Lakes. Inland- 180 days of service in the deck department. Service gained in the engine room on vessels not more than 200 GRT, may be creditable for up to 25% of the deck service requirements for Mate. There are also tonnage, sail, and commerical assistance towing requirements. Other requirements include completing a First Aid course, and a CPR course. All candidates must complete an examination.