A blue hole is an underwater sinkhole formed in the ice age by weather conditions beating against what was then a shallower ocean. At 335 meters, the deepest blue hole recorded is in Mexico and the second deepest is Dean’s Hole in the Bahamas at 202 feet (source). Sink hole jumping is popular among a particularly daring group of underwater free-divers who get their kicks from jumping head first into
these deep, dark caves without any kind of breathing support or equipment. It already sounds scary, but wait … there’s more: “[in blue holes] water circulation is poor, and they are commonly anoxic below a certain depth; this environment is unfavorable for most sea life, but nonetheless can support large numbers of bacteria.” (source) A variety of fossils have been found in Dean’s Hole including the remnants of crocodiles, tortoise and even a human tibia.
A number of free-divers have jumped into these gaps in the earth and have reached incredible depths considering it is all done with one breath:
Recently, the above video was made documenting a jump by Guillaume Nery from France. There is a disclaimer on the Youtube page to clarify that the video was created with artistic intent and has been edited. Even so, it’s pretty fantastic – and absolutely terrifying.
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