A team of explorers say they have discovered the world's deepest underwater cave, at least 1,325ft down, near the eastern Czech town of Hranice.

Polish adventurer Krzysztof Starnawski said he felt like a "Columbus of the 21st century" after making the discovery.

Mr Starnawski, 48, made the claim over the flooded limestoneHranice Abyss, which he has explored since 1998.

On Tuesday, he dived to a narrow slot at a depth of 200 metres and let through a remotely-operated underwater robot, or ROV, which reached 404 meters.

When the robot reached this point, "it was as deep as its rope could go, but the bottom was still nowhere in sight", the Czech Speleological Society said.

The society thinks the cave is even deeper and will yield additional records.

In 2015, Mr Starnawski himself passed through the slot and went to 265 metres' depth, realising that he was still far from the bottom and that the cavity was widening.

He said the discovery made the Hranice Abyss the world's deepest known underwater cave, beating the previous record-holder, the Pozzo del Merro flooded sinkhole in Italy, by 12 metres.

Diving in the cave is a challenge because of muddy conditions and water as cold as 7C, as well as a mineral composition which damages equipment and hurts any exposed skin.

"But that is the only price to be paid for this discovery and it was worth paying," he said.

Today, Mr Starnawski will dive to 200 metres to bring the robot back though the narrow passage. The device was specially made for the expedition by a Polish firm, GRALmarine.

He said National Geographic, which first reported the discovery, covered some €20,000 of the cost of the project.

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