We bought the disposable Kodaks for our barrier reef trip. They suck and you won't be happy with the quality. You don't necessarily need to buy one though. In Australia we were able to rent a very nice underwater cam for $60 ($40 first day, $20 second) with a 2gb card. They burned a dvd with all the photos when we turned it in.
Since you have a few days, google "underwater camera rental" +Florida and you should turn up tons. This will get you a top of the line cam without the full cost, and no film developing. With digital it is soooo nice to be able to review your pics at lunch to see what turned out, what didn't, and then go retake the ones you want.
Also, with the nicer cames you can record video. We did this and in the picture shows my wife made of our trip the show occasionally cuts to video, I love the effect.