Hranická propast, the Hranice abyss (Photo: Jiří Komárek/CC BY-SA 4.0)
Krzysztof Starnawski, a diver from Poland, found the cave in 1999. Even back then, he knew it was an unusual cave: the water made the team’s skin itch. Carved from limestone, the cave was shaped by “hot water saturated with carbon dioxide [that] bubbled up like a volcano” from the cave bottom, reports National Geographic, which funded the expedition.
The question was: where was the bottom?
Now, Starnawski and his team—with a major assist from an underwater robot—have found it, 1,325 feet deep, making this cave the deepest underwater cave in the world.
Previously, that record was held by Pozzi del Merro, an underwater sinkhole in Italy. This cave is in the eastern Czech Republic, where the country borders Poland and Slovakia.
To find the bottom of the cave, Starnawski dove down around 650 feet to a small break in the floor of the cave’s upper section. He’d previously been through, only to realize the cave went down, much, much further. This dive, he directed a ROV through the slot, from which it traveled all the way down.
Without the robot, it would not have been possible to get to the bottom of the cave; the deepest scuba dive on record went just over 1,090 feet deep.