We visited 3 places in Belize and Gumbo Limbo was our favorite booking. It is on the more southern end of the island, so it was more quiet and out of the more hectic areas. The cabaña itself was clean and cute. There was ample natural light and windows provided a nice breeze (there was an A/C unit in the bedroom too). Ben and Aria were extremely friendly and very quick at responding to questions. They gave a several tips that proved to be well worth the experience! While they were available for questions/help, we also had privacy to relax. They have bikes available for use and friendly dogs in the yard. We would book again with them in a heart-beat.
We loved snorkeling with Carlos' catamaran but they feed sharks (an ecological no-no), so another option is Raggamuffin. We also love stand-up paddleboarding with Contour.