I have not tried these options but I did save a few posts from the board in my Belize file for future reference on such events.
For snorkeling/beach BBQ, it would be Tulu! He's like a little fish in the water and great with beginners. For a fun day sail (or a sunset cruise), call George Eiley. His boat is the Rum Punch. Both been on the island forever and lots of fun!
web site fishingsanpedro.com tel 501-2262835 tell Steve you want a fishing , snorkel ,fresh fish/lobster bbq day and you want to get in the water to watch and can you help? he will hook you up with a great local 2 man team capt and mate who will make you so happy