The world's greatest freediver, Natalia Molchanova, is feared dead after disappearing while diving recreationally off the coast of Spain.
Despite her skill to swim deeply while holding her breath, her family and peers have braced for the worst.
"It seems she'll stay in the sea. I think she would like that," her 28-year-old son, Alexey Molchanova, also a champion freediver with a total of 4 world records, told The New York Times.
Another champion freediver, William Trubridge, said he has already begun mourning Molchanova, a Russian national.
"The world lost its greatest freediver on Sunday, and my friend Alexey lost his dear mother, teacher, and training... " he Tweeted on Tuesday.
The world lost its greatest freediver on Sunday, and my friend Alexey lost his dear mother, teacher, and training... http://t.co/5jmgHCt3YU— William Trubridge (@WillTrubridge) August 4, 2015
A joint statement by Molchanova's family and AIDA, the international diving federation, said the 53-year-old Russian athlete went diving on Sunday without fins at a depth of at a depth of 30-40 meters (approximately 100-130 ft) off the coast of Formentera and hasn't been seen since.
An alert was raised after 5 p.m. Sunday, and within minutes, special underwater police were deployed from the neighboring island of Ibiza, ESPN reports.
Maritime rescue coordinator Miguel Chicon described the operation as "very complicated," according to the Associated Press. He explained that Molchanova could have become trapped by weights she was wearing at the time of the dive.
On Wednesday, Spain's rescue services called off their underwater search and said they would limit their operations to monitoring the surface of the Mediterranean Sea instead.
Molchanova's family has enlisted a remote-controlled submersible robot to continue the underwater portion of the search, police said.
Molchanova is the most decorated freediver in the world. She has 41 world records and 23 world champion titles to her name. Last September she broke the world record for dynamic freediving, swimming 778 feet using just one breath and a monofin.