Most of the sites are pretty much the same, canyons. Lots of Nurse sharks, Grouper ect. I have been to a few of them a couple of times within a few days and saw completely different fish. I went with Ecologic divers and they wanted us to max out in the 75 fsw range, although you can get a lot deeper. Expect vis about 40 to 100+ depending on weather. Who are you planning on going with, as far as I know only two places pump air and nitrox and they supply all the other dive ops. Be carefull who you go with, I have heard horror stories about a few of the operations. I lucked out with Ecologic Divers, I had an entire day of just me diving when other people from my hotel had their dives cancelled because they only had three.