(a) An OSV of at least 6,000 gross tonnage, as measured under section 14302 of Title 46, United States Code (hereafter referred to as an OSV of at least 6,000 GT ITC), must apply all regulations of the Coast Guard that depend on the vessel's tonnage using the tonnage as measured under the Convention measurement system.

(b) An OSV that is measured only under section 14502 of Title 46, United States Code, and that is at least 500 gross register tons as measured under that system (hereafter referred to as an OSV of at least 500 GRT), must apply all regulations of the Coast Guard that depend on the vessel's tonnage as if the vessel's tonnage were at least 6,000 GT ITC.

(c) In this subchapter, tonnage thresholds expressed in terms of “gross tons” are applied using GRT, if assigned, and GT ITC if GRT is not assigned.