Photo: Krzysztof Starnawski is seen during five hours of decompression after diving to 215 meters in Hranicka Propast cave, Czech Republic. Photograph by Marcin Jamkowski A team of explorers has found the deepest underwater cave yet discovered, with a bottom that lies at least 1,325 feet below the water's surface.
Polish explorer Krzysztof Starnawski, who led the team, first explored the cave -- named Hranická Propast and located near the Czech town of Hranice -- in 1999, and instantly knew it was an unusual find. He told National Geographic, which sponsored his most recent expedition, that hot water saturated with carbon dioxide bubbled up like a volcano, and made his exposed skin itch.
A series of dives over the years hinted at the abyss' depth. In 2014, he reached 656 feet, thinking he had found the bottom, only to discover a very narrow opening that led to a vertical tunnel. The following year, some of the rock in the cave had crumbled, widening the opening and making it possible for him to squeeze through. He reached a depth of 869 feet and released a probe, which at 1,214 feet landed on what was probably a pile of debris from the collapsed passage above.
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Each time he dived down to such depths, Starnawski had to spend between two and four hours in a dry decompression bell; the only way to explore much deeper was to deploy a Remote-Operated Vehicle (ROV), which his team did during its record-setting mission Tuesday.