I went to the Bahamas for spring break a couple years ago, at the end of March, and it was surprisingly chilly the few days I was there, especially at night. I would pack clothes that you typically wear in the spring and early summer, like shorts, lightweight shirts, etc., but bring a pair or two of jeans and a sweater just in case.
You’ll have fun, as @ducky_dnl said, the water is amazing…I had always assumed that pictures of the water in the Bahamas were photoshopped but nope, that’s really what it looks like! Try to go snorkeling while you’re there, in that water its like you can see for miles. Also, the people there are quite friendly and interesting. Make friends with a bartender during the day before they get busy, they have great stories and love to talk, as do a lot of the female market vendors…they love giving advice about life, whether you asked for it or not, although I’m sure it’s part of the ploy to get you to buy something…but honestly, depending on where you go, the stuff they sell isn’t bad…when I was there I got windchimes, a very beautiful candle, a necklace, and earrings and I get compliments on all of those all the time, so don’t be afraid to buy a few things.
Also, just as a warning, do NOT buy beer there. It is insanely expensive. I’m talking approximately $43 for a case and I’m sure the price has risen since I’ve been there. Rum is dirt cheap though, go figure!