13) Dean's Blue Hole, Bahamas
Dean's Blue Hole is the world's deepest known blue hole with seawater. It plunges 202 metres (663 ft) in a bay west of Clarence Town on Long Island, Bahamas.
Dean's Blue Hole is named after the family name of local landowners. It is located in a small bay, divided from the openbsea with small peninsula. Over the last few years this sinkhole has become a scene of world-class free-diving .