Explorers discovered World’s deepest underwater cave read more at here www.spinonews.com/index.php/item/1089-explorers-discovered-world-s-deepest-underwater-cave

A team of explorers discovered that a cave in the eastern Czech Republic is the world's deepest flooded fissure, going at least 404 meters (1,325 feet) deep.

Polish explorer Krzysztof Starnawski, and his team determined that the flooded limestone Hranicka Propast, have explored for decades in its upper parts, was at least 404 meters deep.

He scuba dived to a narrow slot in the rock formation at 200 meters down, then sent a remotely operated underwater robot that went to the depth of 404 meters, but did not hit the bottom.

In 2015, Starnawski himself went to 265 meters down without reaching the cave's bottom. But, after diving that far down, Starnawski had to spend over six hours in a decompression chamber, and decided he needed a robot instead.

Starnawski said, Hranice Abyss the world's deepest known underwater cavity, beating the previous record-holder, a flooded sinkhole in Italy called Pozzo del Merro, by 12 meters (39 feet).

The Czech Speleological Society, said, the cave is even deeper and will yield additional records. When the robot was 404 meters deep it was as deep as its rope could go, but the bottom was still nowhere in sight.

Starnawski said, diving in the cave is a challenge because it muddy areas and water temperature of 15 degrees Celsius (59 degrees Fahrenheit). The water's mineral composition also damages equipment and injures exposed skin.