August 5, 2015 10:56 AM EDT

The world of free diving is in mourning this week over the presumed death of Natalia Molchanova, a 23-time world champion of the difficult sport who failed to return from a dive on Aug. 2. Though Molchanova had successfully completed dives to depths of hundreds of feet, even the most accomplished free diver puts her life at risk.

Why would anyone voluntarily dive so deep with no extra oxygen and no link to the surface?

Diving in general is as old as swimming, but making a sport out of depth competition is a newer phenomenon. In a 1960 cover story about the rise of skin diving, TIME reported that while anyone could snorkel and dive, “the sport’s aristocrats are the ‘free divers'” who dive without keeping the surface in sight. (In the article’s terms, those free divers were interchangeable with scuba divers, who carried air tanks with them. Skin diving is essentially a step between free diving and snorkeling, in that skin divers will duck underwater completely but don’t necessarily use any specialized tools or training.)

The post-World War II trend had one man to thank for the new trend: Jacques Cousteau. Cousteau had discovered diving in the 1930s while in the Navy, when a friend gave the already-strong swimmer some goggles while they were stationed in the Mediterranean. Cousteau fell in love with what he saw underwater, but was frustrated by the fact that he had to stay near the air. “The problem had badgered divers as far back as 5000 B.C.. when the Sumerians spun the tale of a swimmer who sought the weed of eternal life beneath the waves,” TIME wrote. “Down through the centuries, woodcuts show submerged men hopefully sucking on bags full of air or puffing on tubes reaching to the surface. Looking for something better, Cousteau tried an oxygen lung based on a design developed by the British as early as 1878. He almost killed himself. He did not know the fatal flaw of oxygen: it becomes toxic at depths below 30 ft. Twice Cousteau had convulsive spasms, was barely able to drop his weights and make the surface.”

It was in the 1940s that he developed the Aqua-Lung, the first scuba gear, and in 1953 that his book The Silent World was released in the U.S. to immense success. A few years later, it was turned into an Academy Award-winning color film of the same name. The movie, TIME explained, “opened the world’s eyes to the magic world under the sea, sent both scientists and pleasure seekers hustling for masks and fins to see for themselves.” Diving, whether with a snorkel or scuba gear or the lungs alone, captured the attention of people all over the world.

It was another film, decades later, that spread the word about the non-scuba version of free diving, the type that was practiced by Molchanova: 1988’s Luc Besson drama The Big Blue.

As TIME described in 2002, when free diving lost another of its champions—Audrey Mestre, who drowned off the coast of the Dominican Republic while going for a new world record—the movie was “inspired by real events and featured rapturous cinematography.” About 15 years after its release, there were about 20,000 people competing “in a sport that was barely heard of 15 years ago,” plus a couple dozen who practiced a “no-limits” version, using extra weighted sleds to get down even farther than is possible with the body alone.

Despite the danger, despite what happened to Mestre and to Molchanova, free diving’s practitioners find that the risk is worth it. “[Putting limits on diving] would be like trying to forbid people from climbing Everest,” diver Loic Leferme told TIME in 2002. “It’s impossible.”

Read the full story from 2002, here in the TIME Vault: Lost in the Big Blue

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Write to Lily Rothman at lily.rothman@time.com.

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