Voyages upon which shipping articles are not required.

Although they may be used for the voyage; shipping articles are not required for any voyage by— (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.