The term “passenger vessel” means any vessel having berth or stateroom accommodations for more than 16 passengers.
26 U.S. Code § 4472. Definitions
For purposes of this subchapter—
(1) Covered voyage
(A) In generalThe term “covered voyage” means a voyage of—
a commercial passenger vessel which extends over 1 or more nights, or
a commercial vessel transporting passengers engaged in gambling aboard the vessel beyond the territorial waters of the United States,
during which passengers embark or disembark the vessel in the United States. Such term shall not include any voyage on any vessel owned or operated by the United States, a State, or any agency or subdivision thereof.
(2) Passenger vessel