Last Updated Aug 5, 2015 8:04 AM EDT
LONDON -- It's a sport that, by its nature, tests the very limits of human endurance and frequently finds them. That's what appears to have happened to probably the greatest freediver the sport has ever known, Natalia Molchanova, who disappeared off the Spanish island Formentera near Ibiza on Sunday, CBS News correspondent Mark Phillips reports.
In September 2009, Natalia Molchanova held her breath and dove underwater for a record-breaking 3 minutes and 50 seconds.
"Today, my dive was 101 metres, constant weight," she said, after completing the feat.
That dive was under carefully controlled circumstances. On a single breath, Molchanova followed a wire down an astounding 331 feet, swimming with a fin.
That's twice the height of the statue of liberty.
Molchanova, like the other practitioners of the sport of freediving, found a way of shutting down her body to hold her breath for very long periods of time. She once held her breath for 9 minutes and 2 seconds, another record.
But Molchanova's last dive was not under controlled circumstances. She went underwater off the Spanish party island of Formentera, where swimmers and boats go to play, for a dive that was meant to be a relatively shallow, recreational one.
"She has had numerous accidents before this fatal accident, but she just kept pushing deeper and deeper," said James Nestor, an author who has written about deep freediving.
Molchanova would have used the usual technique, slowing down breathing and heart rate, but on her last dive, there were things she couldn't control.
"My understanding was that the conditions were really rough," Nestor said. "There were currents. There was a lot of boat traffic.
Searchers haven't recovered a body, and the current theory is that Molchanova, who was wearing a weight, is lying on the seabed, too deep for normal scuba divers to reach. Her family has hired a remote controlled submarine to continue to look for her remains.