Picture above is El Zacatón, the largest water-filled sinkhole in the world. Floating grass islands called zacate drift about on the surface of the 350 meter deep pit. (Photo by Art Palmer).

El Zacatón, a vertical cave about 100 meters (328 feet) wide and more than 300 meters (1,000 feet) deep, has been called an "upside down Mount Everest." It could easily swallow New York's Chrysler Building. No one has ever reached the bottom, so it's true depth is unknown.

Two scuba divers attempted to reach the bottom in April, 1994. In the process, Jim Bowden set the record for the world's deepest scuba dive by descending to 925 feet (282 meters). Sadly, his good friend and deep diving mentor Sheck Exley died making the same attempt.

Source

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