I'll admit, I haven't worn a suit over the last week; there aren't many situations in the Caribbean where one is required. Some lightweight sport coats do the trick when needed, but a more important item of clothing is the bathing suit. And getting the fit just right is imperative.
Too long, and you sacrifice aerodynamics when swimming from one end of the pool to the other. Too tight, and people will awkwardly hand you a towel after you emerge, kind of like if you are ever offered a mint (the suggestion should be noted).
My opinion? Short and baggy. Don't worry about showing a little thigh so long as what's required by law to be out of sight, is. There's no sense in being uncomfortable when relaxation is the name of the game. And once you've nailed your swim suit fit, the only thing left to do is grab yourself a rum punch and enjoy.