Lara and I did the PADI underwater photographer course and we bought a little Fuji digital point and shoot and dedicated housing. The results weren't bad but everything revolves around the depth to which you'd be diving. If you're only snorkelling, it won't be an issue, though.
I have a friend at work whose hubby is a dive master and has a Nikonos + lenses / strobes which he "might" be prepared to sell - though I've no idea how much he might want for it. I've asked her to ask hubby and see if it's for sale and, if so, how much he's asking. I've moved quickly as they're about to go to Cuba this weekend for almost 3 weeks (back 29/03) which might be too late for you.
There's absolutely no pressure if you're not interested but it would be a great piece of kit and I doubt it'd be massively expensive if he's prepared to part with it. He uses a big Canon DSLR and bespoke housing / strobes these days, so it's probably in the spare room from one year to the next....