(a) An applicant for an endorsement as master of river self-propelled vessels of unlimited tonnage must meet the same service requirements as master of inland self-propelled vessels of unlimited tonnage.

(b) An applicant for an endorsement as master or mate of river self-propelled vessels, with a limitation of 25 to 1,600 GRT, must meet the same service requirements as those required by this subpart for the corresponding tonnage Great Lakes and inland self-propelled endorsement. Service on the Great Lakes is not, however, required.