Dean's Blue Hole is said to be the deepest blue hole in the world, and the second largest underwater chamber. This warm salt-water swimming pool dips some 663 feet (203 meters) into the ocean floor right offshore. At the surface it is 80 x 120 feet (25 x 35m), but opens out after 60 feet (20m) into a cavern with a diameter of at least 330 feet (100 m).
A school of tarpon hang in the shadows at 65 feet and friendly turtles and tiny sea horses sometimes come into the hole for a break from the ocean currents. The coral caves and sand banks on the side of the entrance harbor all kinds of tropical reef life, from tiny shrimps and colorful tropical fish to groupers and snappers.
It is located northwest of Clarence Town, and is the site where the Free diving World Record was set in April 2007. Experts at Reel divers and Vertical Blue, who have done dives at the site, report that: "It is enclosed on three sides by a natural rock amphitheater, and on the fourth side by a turquoise lagoon and powder white beach. There is never any swell or waves inside the Hole, and visibility is usually between 50 - 100 feet (15 - 30m)."