((a)) Classes of endorsement as qualified members of the engine department on vessels of at least 100 gross tons as measured under , or an alternate tonnage measured under as prescribed by the Secretary under (except vessels operating on rivers or lakes (except the Great Lakes)) may be prescribed by regulation.

((b)) The ratings of wiper are entry ratings and are not ratings as qualified members of the engine department.

((c)) ** .—** The Secretary may classify the merchant mariner credential issued under subsection (a) based on—

((1)) the tonnage and means of propulsion of vessels;

((2)) the waters on which vessels are to be operated; or

((3)) other appropriate standards.

((d)) ** .—** To qualify for a credential under this section, an applicant shall provide satisfactory proof that the applicant—

((1)) is at least 18 years of age;

((2)) has a minimum of 6-months service in the related entry rating;

((3)) is qualified professionally as demonstrated by an applicable examination or educational requirements; and

((4)) is qualified as to sight, hearing, and physical condition to perform the member’s duties.