((a)) This section applies to a vessel of at least 100 gross tons as measured under , or an alternate tonnage measured under as prescribed by the Secretary under except—

((1)) a vessel operating only on rivers and lakes (except the Great Lakes);

((2)) a barge (except a seagoing barge or a barge to which chapter 37 of this title applies);

((3)) a fishing, fish tender, or whaling vessel (except a fish tender vessel engaged in the Aleutian trade) or a yacht;

((4)) a sailing school vessel with respect to sailing school instructors and sailing school students;

((5)) an oceanographic research vessel with respect to scientific personnel;

((6)) a fish processing vessel entered into service before , and not more than 1,600 gross tons as measured under , or an alternate tonnage measured under as prescribed by the Secretary under or entered into service after , and having not more than 16 individuals on board primarily employed in the preparation of fish or fish products; and

((7)) a fish processing vessel (except a vessel to which clause (6) of this subsection applies) with respect to individuals on board primarily employed in the preparation of fish or fish products or in a support position not related to navigation.

((b)) A vessel may operate only if at least—

((1)) 75 percent of the crew in each department on board is able to understand any order spoken by the officers, and

((2)) 65 percent of the deck crew (excluding licensed individuals) have merchant mariners’ documents endorsed for a rating of at least able seaman, except that this percentage may be reduced to 50 percent—

((i)) on a vessel permitted under to maintain a 2-watch system; or

((ii)) on a fish tender vessel engaged in the Aleutian trade.

((c)) An able seaman is not required on a towing vessel operating on bays and sounds connected directly with the seas.

((d)) An individual having a rating of less than able seaman may not be permitted at the wheel in ports, harbors, and other waters subject to congested vessel traffic, or under conditions of reduced visibility, adverse weather, or other hazardous circumstances.

((e)) The owner, charterer, managing operator, agent, master, or individual in charge of a vessel operated in violation of this section or a regulation prescribed under this section is liable to the United States Government for a civil penalty of $10,000.