|Location:||Near Clarence Town on Long Island, Bahamas.|
|Classification:||Karsthöhle Doline or sink|
|As far as we know this information was accurate when it was published (see years in brackets), but may have changed since then.
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Dean's Blue Hole is the world's deepest known blue hole.
Blue hole is a geographic term, which describes dark blue circular spots in the shallow Carribbean sea. They are caused by shafts ending on the sea floor, which are the natural entrances of huge cave systems below. The caves formed during cold periods of the Ice Ages, when the sea level was 100m below todays sea level. As a result most of those blue holes are around 100m deep. This one is exceptional as it is more than 200m deep.
The opening is almost circular with a diameter between 25m and 35m. The walls of the hole are vertical, there are even some overhanging parts where the shaft widens. The waterfilled shaft is used by apnoe divers, which dive as deep as possible along a rope.