have acquired at least 24 months licensed service or equivalent experience on vessels or integrated towing vessels and tows of at least 4,000 gross tons as measured under
section 14502 of this title, or an alternate tonnage measured under
section 14302 of this title as prescribed by the Secretary under
section 14104 of this title, operating on the Great Lakes or oceans, with a minimum of 6 months of that service or experience having been on the Great Lakes; and