An offshore supply vessel certificated under this subchapter that is less than 500 gross register tons (GRT) as measured under section 14502 of Title 46, United States Code, or 6,000 gross tonnage (GT ITC) as measured under section 14302 of Title 46, United States Code when GRT is not assigned, may also be certificated as an oil spill response vessel.
46 C.F.R. §126.225