Code of Federal Regulations Title 46. Shipping § 46.14.203 Voyages upon which shipping articles are not required

(a) A yacht;

(b) A vessel engaged exclusively in fishing or whaling;

(c) A vessel aboard which the merchant mariners are by custom or agreement entitled to participate in the profits or results of a cruise or voyage;

(d) A vessel employed exclusively in trade on the navigable rivers of the United States;  or

(e) A ferry, or a tug used in ferrying, if the vessel is employed exclusively in trade on the Great Lakes, other lakes, bays, sounds, bayous, canals, or harbors.