46 U.S.C. § 7306

1. (a)The Secretary may issue a merchant mariner credential, to members of the deck department in the following classes:
   1. (1)Able Seaman-Unlimited.
   2. (2)Able Seaman-Limited.
   3. (3)Able Seaman-Special.
   4. (4)Able Seaman-Offshore Supply Vessels.
   5. (5)Able Seaman-Sail.
   6. (6)Able Seaman-Fishing Industry.
   7. (7)Ordinary Seaman.
2. (b)The Secretary may classify the merchant mariner credential issued under subsection (a) based on—
   1. (1)the tonnage and means of propulsion of vessels;
   2. (2)the waters on which vessels are to be operated; or
   3. (3)other appropriate standards.
3. (c)To qualify for a credential under this section, an applicant shall provide satisfactory proof that the applicant—
   1. (1)is at least 18 years of age;
   2. (2)has the service required by the applicable section of this part;
   3. (3)is qualified professionally as demonstrated by an applicable examination or educational requirements;
   4. (4)is qualified as to sight, hearing, and physical condition to perform the seafarer’s duties; and
   5. (5)has satisfied any additional requirements established by the Secretary, including career patterns and service appropriate to the particular service, industry, or job functions the individual is engaged.