The World's Deepest Underwater Cave is Almost The Height Of The Empire State Building

Polish explorer Krzysztof Starnawski’s fascination with the Hranická Propast, or Hranice Abyss, an underwater cave in the Czech Republic, began in 1999. The diver, who once held the world record for the deepest dive (283-meters) with a closed circuit rebreather, says the cave’s limestone unusual formation led him to suspect that it was a lot deeper than his dives had taken him.

Armed with a grant from National Geographic, Starnawski and his team returned in 2014. This time, the diver managed to reach 200 meters, or what he thought was the bottom of the cave, only to find a “squeeze passage” in the rock that led to another deep, dark, tunnel. Unable to go any further, he lowered his probe to its maximum length of 384 meters, and still did not hit bottom. Interestingly enough, this was a mere 8 meters shy of Italy’s Pozzo del Merro, the world’s deepest underwater cave.

Believing that Hranická Propast could easily surpass that depth, the 48-year-old Polish cave explorer returned in 2015. This time, Starnawski went through the “squeeze passage” that had widened substantially since his previous visit and swam all the way down to 265 meters. Still finding no bottom, the explorer lowered the probe to 370 meters before it was stopped by a pile of debris, most likely from the collapse of the squeeze passage.

To investigate beyond the rubble, Starnawski returned to the area again in 2016. This time, he was accompanied by a remotely-operated underwater robot (ROV). To give the ROV a good chance to reach the cave’s floor, Starnawski scuba dived 200 meters to install a new line for the ROV to follow. Then on September 27, the team at the surface guided the ROV to the line marker, and watched as it made its way to a record-breaking depth of 404 meters!

While that is enough to grab the title of the world’s deepest underwater cave, the Czech Speleological Society believes the cave is even deeper. They say that the robot was limited by the length of the rope and speculate that the floor of the Hranická Propast goes well beyond 404 meters. Whether that is the case will be revealed soon. That’s because Starnawski and his team are determined to return and continue their quest to unveil all the secrets this mysterious, seemingly unending cave has to offer.

While the Hranická Propast is the world’s deepest underwater cave, it is not the deepest known cave on Earth. That claim belongs to the Krubera Cave. Located in the country of Georgia, it extends an astounding 2,197 meters underground. To put it in perspective, that is deeper than the length of the Burj Khalifa, Eiffel Tower, the Great Pyramids of Giza, the Empire State Building, the Washington Monument, and the Chrysler building, combined!

Resources: phys.org, nationalgeographic.com,abc.ne.au,