The Mystery Of Belize's Beautiful Great Blue Hole

Scuba divers and snorkelers all over the globe head to Belize to see the Great Blue Hole, an underwater sinkhole that runs 410 feet deep and spans 984 feet across. The Great Blue Hole is part of the Belize Barrier Reef Reserve System and is filled with all sorts of marine life, including sharks and groupers (via Belize). It's a UNESCO World Heritage Site as well and is considered the largest sea sinkhole in the world.

For a long time, the Great Blue Hole was only known to the fishermen in Belize. In 1971, however, world-renowned marine biologist Jacques Cousteau studied the hole and called it one of the best diving spots in the world, per Chabil Mar Villas. A NASA scientist, Glyn Collinson, is one of the people who have dived into the Great Blue Hole and described it as "the deepest, deep blue hole imaginable; A chasm that fell away deep into the deep dark, blue" (via Belize). Like other sea holes, the Great Blue Hole was once a cave that ended up underwater about 10,000 years ago at the end of the Ice Age when the sea level began to rise.

In 2018, business magnate Richard Branson, Fabien Cousteau (Jacques Cousteau's grandson), and a team of scientists descended into the Great Blue Hole to find out what lies beneath. The expedition made use of two submarines with high-tech equipment so a 3D map of the hole could be captured. Near the bottom of the hole, the team was able to see stalactites, which are common formations on caves and serves as proof that the cave was once not underwater, according to CNN.

Another interesting find was a layer of hydrogen sulfide at about 300 feet into the hole. Per Erika Bergman, an oceanographer who was part of the team, all the light from above diminishes at about that level and everything turns completely dark. The team was also glad to report that the Great Blue Hole is pretty clean and clear, with just a few pieces of plastic here and there.

Despite the Great Blue Hole's popularity around the world, there are only a few people who have been in its depths, and a few of them never made it out alive. Bergman said that they were able to spot a couple of those people and alerted the Belize government of their location per Business Insider.