For Altun Ha and cave tubing, Tanisha tours, guided by Daniel Nunez. This guy is a walking encyclopedia on local wildlife and culture, has a well run operation, provides snacks, lunch, and drinks. The best.
For snorkeling Shark Ray and Hol Chan, use Mercedes and his son Victor on the glass bottom boat "Reef Seeker". Mercedes watches you closely while you are in the water, snorkels with you, and holds the sharks and rays for you to touch. Really nice guys with a quality operation. Tanisha is downtown, we booked snorkeling thru dive shop at Victoria House.