Bahamas will South Florida weather minus the thunderstorms (but they do happen even though they usually end in September or October). Expect low to mid 80s during the day. The water should still be in the 70s by then if you're lucky. The night time will definitely call for a fleece unless you're from Canada and I can only imagine it gets much colder at sea than on land. But be prepared, it is November, anything can change if a cold front moves in.