(a) In General.—Except as otherwise provided, a vessel may engage in a trade only if the vessel has been issued a certificate of documentation with an endorsement for that trade under this chapter.

(b) Vessels Less Than 5 Net Tons.—A vessel of less than 5 net tons may engage in a trade without being documented if the vessel otherwise satisfies the requirements to engage in the particular trade.

(c) Barges.—A barge qualified to engage in the coastwise trade may engage in the coastwise trade, without being documented, on rivers, harbors, lakes (except the Great Lakes), canals, and inland waters.

(d) Aquaculture Waiver.—

(1) Permitting of nonqualified vessels to perform certain aquaculture support operations.—Notwithstanding section 12113 and any other law, the Secretary of Transportation may issue a waiver allowing a documented vessel with a registry endorsement or a foreign flag vessel to be used in operations that treat aquaculture fish for or protect aquaculture fish from disease, parasitic infestation, or other threats to their health if the Secretary finds, after publishing a notice in the Federal Register, that a suitable vessel of the United States is not available that could perform those services.

(2) Prohibition.—Vessels operating under a waiver issued under this subsection may not engage in any coastwise transportation.