Doolittle's Grotto Site briefing: The depth under the boat is about 40 feet on a gradual sand slope to the wall. The wall here is basically a sand slope from 30 to 140 feet. It is broken up by two parallel ridges of coral each over 50 feet thick. The ridges are riddled with tunnels that allow you to make your way down the wall through them. The big ridge near the boat has four tunnels that lead to a sand bottom valley between the shallow and deep ridges. The second coral ridge has two bigger crevices splitting it into three sections. The top of the outer coral is 60 feet and the deeper crevices will bring you out to a big sand valley at 120 feet. There is usually a big school of horse eye jacks meandering over the reef the entire dive. Big corals and barrel sponges are common about the reef.