Dean's Blue Hole: 663 feet to Bottom

Long Island (global-adventures.us): The Bahamas Island chain holds many treasurers, but the one technical and cave divers are most interested in are the Blue Holes. Dean's Blue Hole stands out from the rest since it is the deepest known underwater sinkhole in the world.

It plunges 663 feet to the ocean floor, making it vastly deeper than other blue holes on the planet. While there is no proof, many scientists today believe that Dean's Blue Hole actually represents two blue holes stacked on top of each other, with the newer one collapsing into the older one.

The blue hole is roughly circular at the surface, with a diameter ranging from 88 – 110 feet (25 to 35 meters). At a depth of 66 feet (20 meters), Dean's widens considerably into a cavern with a diameter of 330 feet (100 meters).

Using Trimix, Jim King took about 11 minutes to descend to the bottom in1992, where he spent 3 minutes to investigate the surroundings. His ascent back to the surface required nearly five hours of decompression at different ceilings. Aside from setting depth records, King’s team also explored several cave passages, some highly decorated, in the shallower portions of the cave. Some of these tunnels run for almost 1,000 feet.

Dean's Blue Hole is a visually impressive site in a bay just west of Clarence Town on Long Island, Bahamas. As with other blue holes, Dean’s is the result of rainwater penetrating the limestone bedrock onto the water table of glacial sea levels during the last ice age, some 15,000 years ago.

The site is known as the perfect spot for free-diving, and it was the location of numerous world free-diving records. In April 2007, William Trubridge broke a free-diving world record in the blue hole reaching a depth of 276 feet (84 meters) without the use of fins.

In April 2008, during the Vertical Blue 2008 free-diving competition, a total of 25 national records and 5 world records were broken Dean's Blue Hole. During the event, William Trubridge did reach 282 feet (86 meters) in the Constant Weight Without Fins category and 354 feet (108 meters) in the Free Immersion category.

In April 2009, Australian Walter Steyn achieved a new national free-diving record of 330 feet (100 meters) at Dean's Blue Hole.