Explorers Discover World's Deepest Underwater Cave

It's at least 12 metres deeper than the previous record holder.

A celebrated Polish diver has discovered the world’s deepest underwater cave, a flooded limestone chasm in the Czech Republic.

Krysztof Starnawksi, lead explorer, established that the abyss, located in the eastern part of the country, is at least 404 metres deep, 12 metres deeper than the previous record-holder, a flooded sinkhole north east of Rome.

Starnawksi told National Geographic, which part funded the expedition: “I scuba dived down to 200 meters just before the ROV’s deployment to put in the new line for the robot to follow.

“The goal was to give the ROV a good start from there to the deepest part of the cave. We are 100 percent sure the measurements were accurate.”

Krzysztof Starnawski

But the cave could be even deeper still.

“There was a black abyss seen below the ROV when we decided to go up,” expedition member Marcin Jamkowski, a Polish photographer, told The Huffington Post US in an email. “The place was full of trees, logs, branches and we did not want the ROV fiberoptic cable to be entangled somewhere.”

Jamkowski added that the ROV had to make the second part of the journey alone because it was too dangerous for divers to plunge to such depths.

“There had been some dives done by the oil industry to such depths (so-called ‘saturation diving’), but they last approximately a month, surface to surface,” Jamkowski told Live Science. “This can never be done in the cave like this one, so the obvious choice was to send the robot where the man can’t go.”

Marcin Jamkowski

Starnawski told The Associated Press that water in the cave is just 15 degrees Celsius and has a mineral content which can damage equipment and skin.

But the diver has been exploring the cave for nearly two decades, so he knew exactly what equipment and clothing he needed to stay safe.

Starnawski wore an electrically heated drysuit with a helmet and took two masks, two breathing systems, two compasses, two flashlights, three cameras, three cutting devices and two reels of thin line.