How Jacques Cousteau Revolutionized Underwater Exploration

In his 1953 book "The Silent World," oceanographer and filmmaker Jacques-Yves Cousteau described the life-altering moment in 1936 when he slipped diving goggles over his eyes and first caught a vision of the undersea world.

At the time, Cousteau was a 26-year-old gunner in the French navy and thought of the ocean only as a salty obstacle during swim lessons. But when he first peered under the clear, shallow water of Le Mourillon Beach in the French Riviera, he was “astounded” by what he saw through the glass—“rocks covered with green, brown and silver forests of algae and fishes unknown to me, swimming in crystalline water… I was in a jungle never seen by those who floated on the opaque roof.”

“Sometimes we are lucky enough to know that our lives have been changed, to discard the old, embrace the new, and run headlong down an immutable course,” wrote Cousteau, who would go on to revolutionize and popularize scuba diving through his inventions and award-winning films and TV shows. “It happened to me at Le Mourillon on that summer’s day, when my eyes were opened on the sea.”

Cousteau was far from the first person to dream of inventing a system that allowed humans to breathe freely underwater. Aristotle, writing in the 4th century B.C., described a diving bell—an inverted container that traps a pocket of air underwater for divers to take a breath while submerged. In the 17th century, astronomer Edmond Halley showed how a large, weighted diving bell could be continually supplied with fresh air from the surface through a hose. 

Interestingly, some of the earliest breakthroughs in self-contained underwater breathing systems were borrowed from firefighting and mining. In the 1860s, a French engineer named Benoît Rouquayrol patented a hose-fed apparatus for breathing fresh air in a smoky room or a poison-filled mineshaft. He then teamed with French navy Lieutenant Auguste Denayrouze to create the first “demand regulator,” a mouthpiece that allowed an underwater explorer to breathe air from a metal container of compressed air worn like a backpack.  

Rouquayrol and Denayrouze’s regulator was remarkably ahead of its time and was mentioned by Jules Verne in his 1870 novel 20,000 Leagues Under the Sea. The scuba-like system didn’t catch on in the 19th century, though, because the steel tanks of the era could only hold enough air for short, shallow dives. 

After that, most diving equipment followed a “hard hat” design. A diver wore a heavy, copper diving helmet secured to an airtight suit. The helmet was connected by a hose to the surface, where “tenders” manually pumped fresh air to the person below. Because of the weight of the helmet and the limited range of the hose, swimming was impossible. Diving helmets only worked for walking on the ocean floor.  

By the time Cousteau first discovered diving in the 1930s, the best options were two systems developed by the French inventor Maurice Fernez, who created underwater breathing devices to save drowning victims. Fernez’s first apparatus was a lightweight mouthpiece (regulator) tethered to the surface by a long air hose. Then he partnered with Yves Le Prieur to replace the hose with a tank of compressed air.  

The “Fernez-Le Prieur apparatus” was a return to the self-contained breathing systems of the 19th century, but now with higher capacity tanks and rubber masks. Still, the system was inefficient, because the tanks released a steady flow of air—rather than on-demand—and divers had to adjust the air pressure by hand to function at different depths.  

As a young man in the French navy, Jacques Cousteau originally wanted to fly airplanes, but his dream was sidelined by a serious car accident in which he broke both of his arms. He began swimming to recover from his injuries and his instructor turned out to be an avid snorkeler. That’s how Cousteau first discovered the wonders of the undersea world.  

Cousteau was also a budding photographer and filmmaker, and he became obsessed with the idea of shooting footage of the incredible hidden world beneath the waves. But to do that would require an improved underwater breathing apparatus that enabled unrestricted movement and much longer dives.  

All of the existing systems had flaws, some of them potentially fatal. While doing underwater repair work for the Navy, Cousteau’s Fernez air hose disconnected while he was 40 feet below the surface, and he was lucky to make it back alive. Cousteau also experimented with an early “rebreather,” a type of closed-loop regulator that didn't emit exhaust bubbles. What he didn’t fully understand at the time was that the pure oxygen used in rebreather systems became toxic at lower depths. He went into convulsions and lost consciousness while 45 feet underwater, but was pulled to safety at the last minute.  

“Cousteau and his diving buddies were figuring it out along the way,” says Jon Council, former president of the Historical Diving Society. “They were learning, but there was a lot that they still didn’t understand about decompression sickness—what they called the ‘bends’—and other risks.” 

For Cousteau, the best existing option was the Fernez-Le Prieur apparatus, but the continuous flow of air meant that the tanks ran out of air quickly.  

“We wanted breathing equipment, not so much to go deeper, but to stay longer,” wrote Cousteau in The Silent World, “simply to live a while in the new world.” 

It was Cousteau’s first wife, Simone Melchior—a skilled and adventurous diver in her own right—who made the connection that changed the world of diving forever. During World War II, Simone’s father was an executive at a French company called Aire Liquide, which specialized in compressed gasses. Simone wrote a letter to her father, asking if anyone at Aire Liquide was familiar with the idea of a demand regulator. He knew just the guy. 

In late December 1942, during the German occupation of France, Cousteau traveled to Paris to meet with an engineer named Émile Gagnan. During the occupation, Aire Liquide was tasked with manufacturing oxygen tanks and regulator valves for German airplane pilots, but Gagnan was also trying to help his fellow countrymen. Gasoline and diesel fuel were in short supply in France, so Gagnan was looking for ways to use tanks of compressed natural gas in cars and trucks.  

Before he met Cousteau, Gagnan had never thought about diving equipment. He couldn’t even swim. But when Cousteau entered Gagnan’s office and described what he was looking for—a valve that supplied the right amount of air at the right pressure, but only when a diver took a breath—Gagnan knew precisely what he meant.  

“As legend has it,” says Council, “Émile Gagnan reaches into a drawer, plops this thing on the top of his desk and says, ‘Something like this?’”  

Gagnan had already created the very same demand valve for his natural gas conversation kits. It was designed to release just the right amount of fuel when a driver pushed the gas pedal. With some simple adjustments to make it waterproof, Gagnan was confident that it would work for Cousteau’s underwater breathing system.  

Cousteau and Gagnan called their new regulator the Aqua-Lung.  

After a brief test run in a frigid Parisian river, Cousteau took his first real dive with the Aqua-Lung in June 1943 in the crystal-blue Mediterranean. It worked exactly as Gagnan had promised. With each inhale, the Aqua-Lung supplied a smooth stream of air at the exact right pressure. And with each exhale, it emitted a bloom of bubbles that rose to the surface.  

“I experimented with all the possible maneuvers of the Aqua-Lung—loops, somersaults and barrel rolls,” wrote Cousteau. “I stood upside down on one finger and started laughing, a shrill distorted laugh. Nothing I did altered the automatic rhythm of air.” 

“From this day forward, we would swim across miles of country no man had known, free and level, with our flesh feeling what the fish scales know.” 

With the invention of the Aqua-Lung, Cousteau and Gagnan created an underwater breathing system that enabled true freedom and autonomy in the water. No helmets, no air hoses, no adjusting pressure valves for different depths—just swimming and breathing. The impact of the Aqua-Lung on the diving world was immediate.  

“It was like flipping a switch with the public,” says Council. “Your choice before was to hold your breath or use a diving helmet. What the Aqua-Lung did was open up the sea for anyone who wanted to go. It made it possible throw on a rig and walk into the water at the beach or hop over the side of a boat. And once you’re in the water, you’re not restricted in any way—you could swim freely throughout the water column.”  

By the 1950s, diving enthusiasts could walk into a sporting goods store and buy a complete scuba rig for $150 (about $2,000 today).  

Not only did the Aqua-Lung launch recreational diving as a sport, but it also completely changed the way that scientists conducted marine research. Before scuba, marine biologists mostly studied creatures that were pulled up in fishing nets, says Joe Hoyt, a maritime archaeologist with the U.S. National Oceanic and Atmospheric Administration (NOAA).  

“With the Aqua-Lung, researchers suddenly had access to a whole new biome they could actually visit,” says Hoyt. “It was like 70 percent of the planet had been virtually inaccessible and now the doors were open.” 

The Aqua-Lung was only the beginning of Cousteau’s impact on the world of diving and underwater exploration. He was best-known for his films and TV series that introduced millions of people worldwide to the incredible biodiversity of the oceans.  

His 1956 film, “The Silent World," was the first documentary to win the Palme d’Or at the Cannes Film Festival. It also won the Academy Award for “Best Documentary Feature Film.” His popular TV series “The Undersea World of Jacques Cousteau” aired from 1968-1976 and followed the adventures of Cousteau—in his trademark red fisherman's cap—and the crew of his research vessel, the Calypso.  

As Cousteau traveled the world for his TV show, he became increasingly concerned with the impact of human activities on the health of the oceans. In 1973, Cousteau founded The Cousteau Society, a nonprofit organization dedicated to marine exploration, conservation and restoration.  

“Back in the '60s and '70s, Cousteau was part of the early environmental movement, which was pretty novel at the time,” says Hoyt. “Seeing the pollution and damage to the oceans firsthand, Cousteau issued a call to action for conservation. I think that may be equally as impactful to the world of ocean exploration as the technology and TV shows."