This story was updated on August 5 to reflect a change in development.
Champion freediver Natalia Molchanova is missing after failing to surface from a dive on Sunday in the Balearic Sea, near Spain, according to the New York Times.
Molchanova set 41 world records and claimed 23 world champion titles after switching from competitive swimming to freediving in her 40s. Her record for diving without fins is about 233 feet, set last May.
The 53-year-old Russian did not emerge after a recreational dive to about 115 feet. The Coast Guard, private boats, and a helicopter were deployed when she failed to surface. On Tuesday, the search was expanded to include underwater robots.
“She was a freediving superstar, and we all thought nothing could harm her,” Kimmo Lahtinen, president of the global federation for freediving, the Association Internationale pour le Développement de l’Apnée, told the New York Times. “But, you know, we are playing with the ocean, and when you play with the ocean you know who is the strongest one.”
UPDATE: AUGUST 5, 11:30 MDT: Alexey Molchanov, her son, said that he does not expect Molchanov to be found alive, according to the New York Times.