Natalia Molchanova (53), widely regarded as the greatest free diver in history, was missing in the Balearic Sea after diving with three others there on Sunday, according to her son, Alexey Molchanov, and the global federation for free diving.
Molchanova, a Russian who holds dozens of world records, did not surface after a recreational dive to about 35m (about 115ft) without fins off the coast of Formentera, an island near Ibiza.
Her record in that discipline, in which divers use the breaststroke to swim as deeply as possible on a single breath, is 71m (about 233ft), set in May in Dahab, Egypt.
She set the record along a line used to measure depth and to tether the diver in case of emergency.
Unpredictable currents
On Sunday, she was diving recreationally two miles west of La Savina at Poniente de es Freus, a part of the sea where currents at the surface and at depth can be unpredictable and powerful.
When she failed to surface after her dive, her fellow divers conducted a brief search before calling for help via radio.
A flotilla of private boats and the local coast guard deployed.
Air support was added from a Helimar 213 helicopter, and the search lasted until dark. It resumed on Monday morning.
Molchanova remained missing on Tuesday, when the search expanded to include the use of underwater robots capable of searching a radius of nearly 500 miles at depth. They were deployed by a company hired by Mr Molchanov, who is also a competitive diver.
New York Times