Oil tanker, aircraft carrier...vessels under power must give right-of-way to those not under power. If Amos is run over by, say, the USS Ronald Reagan, it would be because the captain of the power vessel violated the rules of road. Sure, Amos would be aground -- the screws would see to that -- but the Captain would probably receive a letter of reprimand or something. So if there's a supertanker and Amos on a collision course the supertanker would give way to Amos.