Watch freediver Guillaume Néry plunge deep into a blue hole abyss off the coast of Long Island, Bahamas. A “blue hole” is a term for a water-filled sinkhole with an entrance below water level.

Seen here is Dean’s Blue Hole, the world’s deepest known salt water blue hole. It plunges 202 metres (663 ft) in a bay west of Clarence Town on Long Island, Bahamas.

Dean’s Blue Hole is roughly circular at the surface, with a diameter ranging from 25 to 35 metres (82–115 ft). After descending 20 metres (66 ft), the hole widens considerably into a cavern with a diameter of 100 metres (330 ft). [source]