More blue holes than anywhere on earth, over 200 on and around one island, plus the third-longest barrier reef in the world…More blue holes than anywhere on earth, over 200 on and around one island, plus the third-longest barrier reef in the world running along its east coast and then falling off a wall into the Tongue of the Ocean, a 1,800m-deep trench that comes within a mile of the beach. Sponges, black coral and pelagics on the drop. Andros's blue holes were mapped by pioneering cave divers including Rob Palmer from the 1980s and hold stratified anoxic water that preserves fossils and archaeology, including Lucayan remains. The Tongue of the Ocean has been used by the US Navy's AUTEC underwater testing range since 1966, parts of the water are restricted. Anchorage: Andros has extensive shallow bight anchorages on the west side; the wall is off the east coast. Cave diving requires specific certification and local guides. Hazards: No site-specific hazards noted, brief normally. Altro