I spent a week diving with Amigos Del Mar and enjoyed it very much. In particular, Tony is a master of his craft.
Barefoot Watersports enjoys a very fine reputation and I think they have receintly brought in a new boat or two (someone correct me if I'm wrong).
Gaz Cooper is a role model divemaster/instructor. I should be so good.
Enjoy, my friend. Belize has some truely outstanding diving to offer.