46 U.S.C. § 8301: Minimum number of licensed individuals

Each of those vessels propelled by machinery or carrying passengers shall have a licensed master. in the case of a vessel other than a mobile offshore drilling unit, if on a voyage of less than 400 miles from port of departure to port of final destination, the vessel shall have 2 licensed mates; and in the case of a mobile offshore drilling unit, the vessel shall have licensed individuals as provided by regulations prescribed by the Secretary under section 8101 of this title . A vessel of at least 200 gross tons but less than 1,000 gross tons as measured under section 14502 of this title , or an alternate tonnage measured under section 14302 of this title as prescribed by the Secretary under section 14104 of this title and propelled by machinery shall have 2 licensed mates. A vessel of at least 100 gross tons but less than 200 gross tons as measured under section 14502 of this title , or an alternate tonnage measured under section 14302 of this title as prescribed by the Secretary under section 14104 of this title and propelled by machinery shall have one licensed mate. However, if the vessel is on a voyage of more than 24 hours, it shall have 2 licensed mates. A freight vessel or a passenger vessel of at least 300 gross tons as measured under section 14502 of this title , or an alternate tonnage measured under section 14302 of this title as prescribed by the Secretary under section 14104 of this title and propelled by machinery shall have a licensed engineer. An offshore supply vessel of less than 500 gross tons as measured under section 14502 of this title or 6,000 gross tons as measured under section 14302 of this title on a voyage of less than 600 miles shall have a licensed mate. If the vessel is on a voyage of at least 600 miles, however, the vessel shall have 2 licensed mates. An offshore supply vessel of at least 6,000 gross tons as measured under section 14302 of this title on a voyage of less than 600 miles shall have at least two licensed mates, provided the offshore supply vessel meets the requirements of section 8104(g)(2). An offshore supply vessel of at least 6,000 gross tons as measured under section 14302 of this title on a voyage of at least 600 miles shall have three licensed mates. An offshore supply vessel of more than 200 gross tons as measured under section 14502 of this title , or an alternate tonnage measured under section 14302 of this title as prescribed by the Secretary under section 14104 of this title , may not be operated without a licensed engineer. Subsection (a) of this section does not apply to a fishing or whaling vessel, a mobile offshore drilling unit when on location, or a yacht. suspend any part of this chapter during a national emergency proclaimed by the President; and increase the number of licensed individuals on a vessel to which this chapter applies if, in the Secretary’s judgment, the vessel is not sufficiently manned for safe operation. The Secretary may prescribe the minimum number of licensed individuals for an oil spill response vessel.