The man who taught humans to breathe like fish

Jacques Cousteau’s invention of the aqualung opened the undersea realm to scientists and the public.

Becoming Cousteau, now playing in theaters, begins streaming on Disney+ November 24th.

“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 pillars disappeared beneath the water’s surface. It was cool there but barren—a man-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’s surface the pier was a dull structure of warped wood and chipped paint. Below the surface it abounded with life—orange and yellow corals wrapping around the columns, lush sea plants undulating in the current, schools of silvery fish darting between the posts. 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 exploring more of the ocean, of seeing its wonders for himself.  

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

Although Cousteau learned to swim when he was four, 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. As part of his recovery fellow naval officer Philippe Tailliez suggested he try ocean swimming. 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,” he later said. He’d discovered “a huge and completely untouched domain to explore.”

“I understood that from that day on, all my free time would be devoted to underwater exploration.”

Eventually he could go as deep as 60 feet and stay there for some 70 to 80 seconds. But that wasn’t long enough or deep enough for Cousteau. “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.

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 goes deeper, 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, who specialized in high-pressure pneumatic design. 

It was the middle of World War II and Germany controlled most of France. Gagnan worked for the country’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 two 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,” wrote Cousteau 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 Aqualung made it easier to breathe by balancing ambient and internal pressure, it couldn’t prevent what early divers called the “rapture of the deep”—nitrogen narcosis, when bubbles of nitrogen develop in the bloodstream as the diver descends. To Cousteau, it was “an impression of euphoria, a gradual loss of reflex control, 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.” 

Nitrogen narcosis could be deadly. After the war 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 demonstrate that the Aqualung would allow divers to go more than 100 meters deep. But the person to make the initial attempt, first mate Maurice Fargues, died. He’d lost consciousness at 120 meters (390 feet) and had been 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. They deployed the Underwater Research Group to clean up the deadly aftermath of World War II in the Mediterranean. The Navy divers removed mines cleverly hidden near busy harbors. They retrieved dead pilots from downed airplanes. They witnessed the underwater destruction of a war that had encompassed the sea’s entire coast.   

“I put the thing on, and I went right to the bottom of the pool,” recalls Doubilet, who would go on to photograph the Sargasso Sea, the Great Barrier Reef, and much of the ocean in between for more than 70 National Geographic feature stories. “I was plastered on the bottom, but I was breathing, and it was just heavenly.”

“The Aqualung regulator meant a passport to 70 percent of our planet,” says Doubilet. “This is 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 suddenly surrounded by sharks. Based on his passionate viewing of Cousteau’s documentaries, he recognized them as harmless basking sharks and jumped in the water to swim with them.

When Ballesta returned home, he told his parents what had happened, but they didn’t believe him. “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 was the first to photograph the prehistoric coelacanth underwater. Most recently, he recounted for National Geographic an 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.

Podcast: The Gateway to Secret Underwater Worlds
Listen Now

(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 87 in 1997.  “My job was to show what was in the sea—the beauties of it—so that people would get to know and to love the sea,” Cousteau wrote. 

It’s a world that despite his pioneering contributions and international influence is still largely unknown. According to the National Oceanic and Atmospheric Administration, more than 80 percent of our planet’s oceans remain unexplored. 

In the 78 years since Cousteau and Gagnan invented the Aqualung, more than 28 million people have followed him 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.

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