Dean's Blue Hole
Dean's Blue Hole is a blue hole located in The Bahamas in a bay west of Clarence Town on Long Island and is the world's second deepest, after the Dragon Hole in the South China Sea, with a depth of . Hours - Visitors are asked to respect the hours posted, as access to the location is by use of a private road. 8am - 6pm Formation. A blue hole is a water-filled sinkhole with the entrance below the water level. They can be formed in different karst processes, for example, by rainwater soaking  through fractures of limestone bedrock onto the watertable. Sea level here has changed: for example, during the glacial age during the Pleistocene epoch (ice age), some 15,000 years ago, sea level was considerably lower. Dean's Blue Hole is roughly circular at the surface, with a diameter ranging from . After descending , the hole widens considerably into a cavern with a diameter of .