You are right there are so many to choose from but the ones you really should not miss are
Hol Cham Marine reserve snorkel in the cut probably the best snokeling trip you will ever do, it packed with all sorts of fish and corals.
Shark Ray Alley Snorkel
8ft of water laden with Nurse Sharks and Sting Rays and lots of schools of fish
some of my favorite sites
Cyprus Gardens excellent site 50ft lots of Groupers and Nurse sharks and nice corals
Tackle box is also a great marine life dive as well as Eagle Ray canyons which is located in the marine reserve
I could go on but will let others have a butchers at it