(a) This subpart applies to crewmembers on the following vessels in the navigable waters of the United States en route to a U.S. port or place of destination or at a U.S. port or place:
(1) A foreign vessel engaged in commercial service, and
(2) A U.S. vessel engaged in commercial service and coming from a foreign port or place of departure.
(b) This subpart also applies to the operators of the vessels listed in paragraph (a) of this section.