If you take one of the snorkeling tours, bring an underwater camera with you. If you do not have one, you can buy a plastic disposable camera at the shops in the island.
Most tours consists of two or three dives in different sites. If you did not bring the camera, do not worry, you will be met by an underwater photographer during your dive, who will take a picture of you feeding the fish, and sell it to you once the tour is finished.
If you do not want to get wet, you can take a Glass bottom tour, or join one of the Atlantis submarine tours. This 48-seat real submarine takes visitors on an underwater tour difficult to forget.