There is a detailed map of Caye Caulker that also shows the reef and snorkeling sites. You can buy it at most gift shops.
Everyone snorkels for fun for free at the split and around. There is three sink holes to the back that you can snorkel over. You can cross the split and snorkel the mangroves. Rent snorkeling gear or bring your own and snorkel around docks. Lots of tropical fish like to use the shade. We made a small artificial reef under our dock. Octopus, lobster, shrimp and juvenile fish hide in the old cement bricks, that are now encrusted in different corals growing. Eagle rays and sting rays visit at night looking for food.