Subchapter B - Transportation by Water

26 USC 4471 - Imposition of tax

(a) In general 
There is hereby imposed a tax of $3 per passenger on a covered voyage.
(b) By whom paid 
The tax imposed by this section shall be paid by the person providing the covered voyage.
(c) Time of imposition 
The tax imposed by this section shall be imposed only once for each passenger on a covered voyage, either at the time of first embarkation or disembarkation in the United States.

26 USC 4472 - Definitions

For purposes of this subchapter
(1) Covered voyage 

(A) In general 
The term covered voyage means a voyage of
(i) a commercial passenger vessel which extends over 1 or more nights, or
(ii) 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.

(B) Exception for certain voyages on passenger vessels 
The term covered voyage shall not include a voyage of a passenger vessel of less than 12 hours between 2 ports in the United States.
(2) Passenger vessel 
The term passenger vessel means any vessel having berth or stateroom accommodations for more than 16 passengers.