The man who taught humans to breathe like fish

“Look,” my son said.

We were bobbing in the shadow of a pier on Isla Vieques in Puerto Rico. Wooden slats a few feet above our heads sheltered us from the tropical sun. Weather-beaten pilings disappeared beneath the water’s surface. It was cool there but barren—a human-made spot suitable only for a quick rest during our first foray into snorkeling.

Will pointed down. His eyes were wide behind his mask. He dipped his head underwater. I followed.

We entered another world. Above the water the pier was a dull structure of warped wood and chipped paint. Underwater it teemed with life—orange and yellow corals wrapping around the pilings, lush sea plants undulating in the current, darting schools of silvery fish. This narrow place beneath a dock built decades ago for U.S. warships was as fecund as any jungle—but unlike a jungle, we could float in the midst of it and examine it from every angle.

We had never imagined being surrounded by so much wildlife—and yet it wasn’t enough for Will. “That was so cool,” he said, as we drove back to the hotel in our guides’ rattletrap pickup truck. “I want to try scuba diving.” He didn’t want to be tied to the surface by our rented snorkels. He dreamed of diving deeper, of seeing more of the ocean for himself.

(See five ways Cousteau pushed to protect the environment.)

Such a dream is possible—even ordinary—because of an extraordinarily simple device co-created by Jacques-Yves Cousteau, the French explorer known for his films, his TV shows, and marine conservation. Cousteau made his motto, “Il faut aller voir—We must go and see for ourselves.” With his 1943 co-invention of the Aqua-Lung, the first safe self-contained underwater breathing apparatus (scuba), he invited ordinary people to take that motto as their own, to experience the undersea world for themselves.

Cousteau learned to swim when he was four, but his earliest ambitions aimed at the sky, not the sea. In 1930 he entered the French naval academy to become a pilot, a dream sidetracked by a nearly fatal car accident that fractured both his arms. Fellow naval officer Philippe Tailliez suggested Cousteau try ocean swimming to help his recovery. Tailliez loaned him a pair of goggles and took him spearfishing in the Mediterranean near Toulon, France.

Swimming with the goggles was a revelation: “As soon as I put my head underwater, I got it, a shock … I understood that from that day on, all my free time would be devoted to underwater exploration.”

Eventually Cousteau could go as deep as 60 feet and stay there for up to 80 seconds. But that wasn’t long enough or deep enough for him. “Always I rebelled against the limitations imposed by a single lungful of air,” he wrote in a 1952 article for National Geographic, his first for the magazine.

In the 1930s the options for deepwater diving were few. Mobility in the diving suits the French called pieds lourds (heavy feet)—rubberized canvas suits with a copper helmet and lead-soled shoes—was restricted by the length of the hose supplying air from the surface. An autonomous breathing device created by Yves Le Prieur in 1925 freed divers from the cumbersome hose, but the air supply ran out quickly because of its continuous flow, limiting time underwater.

Cousteau had to come up with his own solution. “I became an inventor by necessity,” he said.

To go deeper, he needed a device that would provide breathable air that also matched the pressure of the water: As a diver descends, the pressure increases, reducing the volume of air in the body and potentially causing the lungs to collapse. Cousteau’s father-in-law put him in touch with engineer Émile Gagnan, an expert in high-pressure pneumatic design.

It was the middle of World War II, and Germany controlled most of France. Gagnan worked for France’s largest commercial gas company, in Paris, where he’d designed a valve that regulated fuel flow, allowing cars to operate on cooking oil, an essential wartime adaptation when the Nazis had commandeered all the gasoline for motor vehicles.

When Cousteau traveled to Paris in 1942 to explain the air pressure problem to Gagnan, the engineer thought his gas regulator could be the solution. Together they tinkered until they had something they could test, a regulator attached by tubes to three canisters of compressed air. Cousteau took the prototype for a swim in the Marne River, east of Paris. “I took normal breaths in a slow rhythm,” he said, “bowed my head, and swam smoothly down to 30 feet.”

The device worked—while he was horizontal. When he was upright, it leaked air. Cousteau and Gagnan rearranged the intake and exhaust tubes to be at the same level. Eventually they had a version that Cousteau felt comfortable trying out in the sea.

Over the course of many months in 1943, Cousteau, Tailliez, and their friend Frédéric Dumas cautiously tested the device they were calling the Aqualung. They made more than 500 dives in the Mediterranean, going a little deeper each time. By the onset of autumn they’d reached 130 feet. By October Dumas had descended 90 feet more.

“The best way to observe a fish is to become a fish,” Cousteau wrote in that first National Geographic article. “And the best way to become a fish—or a reasonable facsimile thereof—is to don an underwater breathing device called the Aqualung. The Aqualung frees a man to glide, unhurried and unharmed, fathoms deep beneath the sea.”

Nearly 80 years after its invention, the same basic design is still in use. “It’s as simple and elegant as a doorknob,” says longtime National Geographic underwater photographer David Doubilet. “It doesn’t fail. In 65 years of diving, I have never had a failure.”

But the ability to plumb the depths exposed divers to other dangers. Although the Aqua-Lung made it easier to breathe by balancing ambient and internal pressure, it couldn’t prevent what’s known as rapture of the deep—nitrogen narcosis, when the nervous system becomes saturated with nitrogen as the diver descends. To Cousteau it was “an impression of euphoria, and then a gradual loss of reflex control, and then a loss of the self-preservation instinct.” To Albert Falco, who sailed with Cousteau for nearly 40 years, “Air takes on a funny taste, and you get drunk on your own breath.”

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Nitrogen narcosis can be deadly. In 1947 Cousteau, who was still in the French Navy as part of its underwater research group, organized autonomous diving tests in Toulon. He wanted to show that the Aqua-Lung would allow divers to go more than 100 meters (328 feet) deep. But the person to make the initial attempt, First Mate Maurice Fargues, died. After passing 120 meters (394 feet), he lost consciousness. He was frantically pulled to the surface but could not be resuscitated. Cousteau was devastated: “I start to wonder if what I’m undertaking makes sense.”

To the French Navy it did. The diver group was deployed by the navy to clear the deadly aftermath of World War II from the Mediterranean, removing mines hidden near harbors and retrieving pilots’ bodies from downed airplanes.

But Cousteau wanted to use his invention to explore, not just salvage. In 1949 he left the navy and soon acquired the Calypso, a former British minesweeper. Adventuring on the ship, he advanced underwater photography, discovering that there, “colors existed as brilliant and as beautiful as any at the surface.” In 1956 Cousteau made the movie The Silent World with a young Louis Malle, who in time would become one of French cinema’s top directors.

David Doubilet saw the film, which won an Oscar, with an uncle and cousin when he was 10. “My eyes grew larger and larger and larger,” Doubilet says. Cousteau became his hero. A year or two later, Doubilet learned to dive in a swimming pool at a beach club in New Jersey: In roughly a decade Cousteau’s groundbreaking Aqua-Lung had been adopted by the public as a recreational pursuit.

“I put the thing on, and I went right to the bottom of the pool,” Doubilet recalls. “I was plastered on the bottom, but I was breathing, and it was just heavenly.”

Doubilet would go on to photograph the Sargasso Sea, the Great Barrier Reef, and other ocean marvels for more than 70 National Geographic feature stories. To him, “the Aqua-Lung regulator meant a passport to 70 percent of our planet”—and Cousteau stands as “a person whose importance to the planet can never, ever be forgotten or underestimated.”

Photographer Laurent Ballesta, who grew up swimming, snorkeling, and scuba diving on France’s Mediterranean coast, was influenced by Cousteau as well. When Ballesta was 16, he was out with friends on a boat when they were surrounded by sharks. Based on his passionate viewing of Cousteau’s documentaries, he recognized them as harmless basking sharks and jumped into the water to swim with them.

When Ballesta told his parents what had happened and they didn’t believe him, he says, “That was the point where I decided that I have to learn photography.”

Since then, Ballesta has discovered a new species of fish called the andromeda goby, and he was the first to photograph the prehistoric coelacanth underwater. Most recently, he recounted for National Geographic a 2019 expedition in which he and his crew lived for 28 days in a pressurized capsule that allowed them to dive for hours in the depths of the Mediterranean.

(In this episode of our podcast Overheard, we chat with photographers David Doubilet and Laurent Ballesta on how they were inspired to follow in Cousteau's footsteps—making discoveries on their own amazing and sometimes terrifying adventures. Listen now on Apple Podcasts.)

Jacques Cousteau remained active in undersea exploration until his death at age 87 in 1997. His job, he once wrote, “was to show what was in the sea—the beauties of it—so that people would get to know and love the sea.” There’s still much to explore: The National Oceanic and Atmospheric Administration estimates that more than 80 percent of the undersea world remains largely unknown.

In the 79 years since Cousteau and Gagnan invented the Aqua-Lung, more than 28 million people have followed them into the ocean and learned to scuba dive.

This spring my son and I will join them. It’s what Will wanted for his 17th birthday—a passport to another world.