Dan in Winnipeg, you are a riot!
But seriously folks, you really have just two options; if the ship is not too far out you can get a water taxi to take you out. This is extremely expensive and will not make you very popular with the Bridge Officers; or you can try to arrange transportation to the next port--also very expensive.
I can't imagine doing it on purpose--but if you did, your options are still the same--or you can arrange transportation home. Just be sure you have your passport with you.