Last time we were down there we did wrecks as a first dive and then, typically, one of the shallow reefs as a second. Watch out for boats that are just doing the reefs and taking snorkellers as well, they will obviously stay shallow and just sit over one patch of reef. If that's OK with you, fine, but you don't want it to be a surprise. Just ask the questions of the dive operation, I'll try to dig out the names of the ones we used as they were very helpful and willing to call other shops to get us the sort of diving we were looking for. If you're willing to drive a little, you will get a lot more choice of dive operation and dive sites. The Speigel Grove is worth a visit as are many of the other wrecks down there. As for the reefs, there's a little pot luck involved, some are in better shape than others, we were fortunate enough to watch 6 or 8 Eagle Rays just cruising around the reef during one of our dives, found Goliath Groupers on others, so you just never know. The reefs themselves are nothing like you will see in some parts of the Caribbean, but the worst day's diving is still better than the best day in the office, right?