John,
That idea from Ghengis' might not be so daft if you were bothered, though I think you'd have to choose your audience or all you'd get is a lot of " how do you hover inverted ? " style questions; with the right P.R. ( and right, preferably non- norwalk virus ridden ship ) it could be a good experience, hopefully pretty much just above sea level.
Another option, I have an Anderson 22 sailing boat, 3 have raced the North Atlantic, a person can't stand up inside though she is otherwise comfortable & well equipped, but she does give a degree of independence, and I wouldn't put on a cabaret every evening unless you really insisted...
DZ