There's lots to photograph here, underwater as well as above. Don't know about female forms though (unless you bring your own) and there aren't many waterfalls on Ambergris Caye!

There are no requirements for novice divers other than the obvious. What are you thinking of? If you're certified you will certainly be allowed to take your camera down with you. But do remember that anything you take diving with you is expendable - if you aren't prepared to lose it don't bring it. Make sure you have insurance that covers flooding. If you don't already have a housing then maybe you aren't experienced at underwater photography, in which case it would be better to spend your money on a decent compact digital camera with housing before you spend a large fortune on an SLR housing.

One hotel that comes to mind for a photographer is Caribbean Villas. Very low density accommodation set in a wildlife sanctuary that has many birds, with an observation platform that looks over the canopy. Xanadu almost next door has a similar ambience. Or I'm sure there are lots of places well north of town that will give lots of wildlife photography opportunities. Victoria House is a good choice, but without the bird sanctuary.

We don't get many "typical touristy" people here - they tend to go to Cancun - and you'll find you quickly relate to the locals.