A Polish explorer says he and his team have discovered the world’s deepest underwater cave, 404 meters (1,325 feet) down, near the eastern Czech town of Hranice.

Krzysztof Starnawski told The Associated Press Friday he felt like a “Columbus of the 21st century” to have made the discovery.

Starnawski found the cave Tuesday in the Hranice Abyss, which he has explored since 1998. He scuba dived to a narrow slot at 200 meters’ depth and let through a specially made underwater robot that went to the depth of 404 meters.

He said that that makes Hranice Abyss the world’s deepest known underwater cave, beating the previous record-holder, Italy’s Pozzo del Merro flooded sinkhole, by 12 meters (39 feet.)

He said some of the costs were covered by the National Geographic, which first reported the discovery .