I once asked a stewardess on a plane (pre 9/11) what would happen if I
refused to give up my ticketed and confirmed seat that I was being
bumped from. She was very quick to quote the list of potential
offences that I could be charged with.

Well, I doubt that holds the same credibility as an order from the Coast
Guard. But most folks aren't interested in the hassles of trying to argue
with the idiots working the airline counters. And someone in a boating
distress situation isn't terribly likely either.