[Dragonfire]

The premier sites are outside of the local diving venues and include Turnoff-Elbow, Turneffe-North & Lighthouse Reef. It's questionable that you'll have the time to do these, but you might want to check anyway. Locally, I'm partial to the far southern sites such as Shark & Ray Alley, Hol Chan Cut & Hol Chan Canyons.
Here is a map for Belize dive sites that I got from the internet