Cousteau and Gagnan Develop the Aqualung

Cousteau and Gagnan developed the Aqualung, a self-contained underwater breathing apparatus (scuba) that allowed divers to descend hundreds of meters below the surface of the ocean for recreation, scientific study, or archaeological investigation.

Summary of Event

Undersea diving Diving, underwater for the purposes of spying, to recover lost treasures from wrecks, or to obtain natural treasures (such as pearls) has been performed since ancient times. The divers of antiquity, however, were able only to remain below the surface for two or three minutes, and the depth to which they could venture was severely restricted. In spite of these limitations, divers are mentioned in Homer’s Iliad (c. 750 b.c.e.; English translation, 1611), and Greek historians—including Herodotus (c. 484-c. 425 b.c.e.)—mention the use of divers by the Greek kings in their many wars. Aqualung
Scuba diving
[kw]Cousteau and Gagnan Develop the Aqualung (Spring, 1943)
[kw]Gagnan Develop the Aqualung, Cousteau and (Spring, 1943)
[kw]Aqualung, Cousteau and Gagnan Develop the (Spring, 1943)
Scuba diving
[g]Europe;Spring, 1943: Cousteau and Gagnan Develop the Aqualung[00760]
[g]France;Spring, 1943: Cousteau and Gagnan Develop the Aqualung[00760]
[c]Inventions;Spring, 1943: Cousteau and Gagnan Develop the Aqualung[00760]
[c]Science and technology;Spring, 1943: Cousteau and Gagnan Develop the Aqualung[00760]
Cousteau, Jacques
Gagnan, Émile

Clearly, once humans discovered the value of diving, many attempts were made to prolong the time it was possible for divers to spend under water. The first device, described by Aristotle in 335 b.c.e., was probably the progenitor of the modern snorkel. It was a bent reed placed in the mouth, with one end above the water. Such devices are useful only for spying or for swimming near the surface of a body of water. Their use is restricted by limits on applicable reed—or snorkel—length and pressure considerations.

The most serious problem associated with pressure occurs because the pressure on a diver’s body increases by about one-half pound per square centimeter for every meter ventured below the surface. For this reason, it becomes impossible to inhale surface air through a snorkel below about 0.9 meters. This restriction results because below that depth, the human chest muscles are no longer strong enough to inflate the chest. In order to breathe at depths below 0.9 meters, a diver must utilize air under pressure, and the air pressure must increase continually as the depth of the dive is increased.

Thus, few changes were made in the technology of diving until air compressors were invented during the early nineteenth century. This invention made it possible for fresh, pressurized air to be supplied to divers. This compressed air could be delivered in amounts that equalized body pressure and the pressure exerted by the water that surrounded the diver. At first, the divers who utilized the method were limited to using diving suits, complete with fishbowl-like helmets. This “tethered” diving made divers relatively immobile. Such diving rigs, however, were very useful when a diver was searching for sunken treasure or performing other complex tasks at a great depth. Tethered diving was especially valuable if a diver needed to remain underwater for a long time.

Shallow-water work, diving efforts of shorter duration, underwater espionage, and recreational diving required less cumbersome outfits and more mobility. Scuba (self-contained underwater breathing apparatus) evolved to meet these requirements. Its development occurred in several incremental leaps forward. In one of the first such leaps, in 1880, Henry Fleuss Fleuss, Henry of England developed an outfit that used a compartmented belt that contained pure oxygen. Belt and diver were connected, and the diver breathed the oxygen over and over.

A modification of Fleuss’s rebreathing system was used by the U.S. Navy for World War II espionage. Nevertheless, the system had three serious drawbacks: The deepest dives it allowed were to depths of 7.6 to 9 meters, pure oxygen was toxic to divers at depths greater than 9 meters, and divers could carry only enough oxygen to allow them to remain submerged for a relatively short period of time. The system did have an advantage for spies, namely that the oxygen—breathed over and over in a closed system—did not reach the surface in the form of telltale bubbles.

The next stage of scuba development occurred when metal tanks, able to hold high-pressure compressed air, were designed. The tanks enabled divers to use air, rather than the potentially toxic pure oxygen. More important, the much increased amount of usable oxygen that a diver could carry in the tanks greatly lengthened the possible duration spent under water. Initially, the main problem with the system was that the air flowed continuously through a mask that covered the diver’s entire face. This process wasted oxygen, and scuba divers expelled a continual stream of air bubbles that precluded clandestine activity.

Working as a team, Jacques Cousteau and Émile Gagnan developed an underwater oxygen regulator that conserved oxygen by releasing only the amount of compressed air that the diver required to breathe. Among the advantages of the Cousteau-Gagnan apparatus was that a mobile diver could stay below the surface for a prolonged time period. As pointed out by Axel Madsen, the problem solved by Cousteau and Gagnan occurred because humans breathe in and out, requiring a scuba mechanism that would prevent a diver from exhaling spent air back into the oxygen supply. The solution was “a valve that would allow inhaling and exhaling through the same mouthpiece.”

It was fortunate for Cousteau that his father-in-law, an executive for Air Liquide Air Liquide —France’s main producer of industrial gases—directed him to Gagnan, an engineer at the company’s Paris laboratory. Gagnan had been developing an automatic gas shutoff valve for Air Liquide, and this valve became the Cousteau-Gagnan regulator Cousteau-Gagnan regulator[Cousteau Gagnan regulator] . With the valve in hand—and funding from Air Liquide—the two men designed a first approximation of their system. Cousteau tested this apparatus in 1943 in the Maine River, but it did not work. By spring, however, additional experimentation led to an acceptable device, which Cousteau and Gagnan patented as the Aqualung. Soon, exhaustive study showed that Aqualungs were suitable for use at depths up to 68.5 meters.

Jacques Cousteau wearing an Aqualung.

(Library of Congress)

This study also identified several perils associated with Aqualung diving. For example, unless divers ascended and descended in slow stages, it was likely that they would get “the bends” (decompression sickness), the feared disease of earlier, tethered deep-sea divers. Another problem was that, below 42.6 meters, divers encountered nitrogen narcosis. This condition led to impaired judgment that could cause fatal actions, including removing one’s mouthpiece or developing an overpowering desire to continue diving downward, to dangerous depths.

Cousteau believed that the Aqualung had tremendous military potential. To get it to the Allies, he traveled to London soon after the Normandy invasion on June 6, 1944. The British, however, did not find Cousteau’s Aqualung particularly important. Cousteau returned to Paris and convinced France’s newly free government to use Aqualungs to locate and neutralize underwater mines laid along the French coast by the Wehrmacht.

Cousteau was commissioned to combine minesweeping with the study of the physiology of scuba diving. Amid this work, he and his colleagues discovered that by using helium-oxygen mixtures in their tanks, they could increase the depth to which a scuba diver could go without experiencing narcosis to 76 meters.


The Aqualung made humans more comfortable under the ocean and sparked a wave of undersea exploration and recreational diving that has greatly enriched the knowledge of the seas. Today, millions of people engage in scuba diving for the purposes of recreation and business. It has made possible developments in marine biology, archaeology, geology, oceanography, historiography, and many other sciences. Moreover, as a popularizer of deep-sea diving through his writing—and later on television and in motion pictures—Cousteau increased the knowledge and experience not only of scientists but also of laypeople, including amateur divers as well as people who merely observed the films and photographs produced by divers. Aqualung
Scuba diving

Further Reading

  • Cousteau, Jacques-Yves. “Fish Men Discover a New World.” National Geographic 102 (October, 1952): 431-472. An interesting, illustrated article that details collaboration with Gagnan in the development of the Aqualung and some of its uses in underwater exploration. Of particular interest to those wishing to learn about the beginnings of scuba diving from Cousteau.
  • _______. “The Ocean, a Perspective.” National Geographic 160 (December, 1981): 780-833. Describes many important aspects of ocean exploration and utilization (for example, mining the sea) using modern tools and methods, including those Cousteau and his collaborators helped develop.
  • Cousteau, J. Y., with Frédéric Dumas. The Silent World. Reprint. Washington, D.C.: National Geographic Society, 2004. An engaging book, made into a motion picture in 1956. Recounts many of the underwater adventures of and explorations by Cousteau and his colleagues from 1938, including postwar efforts at minesweeping along the French coast and development of Aqualung methodology.
  • Fergussen, J. Homer. “Diving.” McGraw-Hill Encyclopedia of Science and Technology. 6th ed. New York: McGraw-Hill, 1987. A brief article on diving that touches many bases succinctly. Topics explored include techniques used in scuba and saturation diving; aspects of diving physiology such as the effects of pressure, nitrogen, oxygen, and carbon dioxide gases; and treatment of the bends.
  • Iverson, Genie. Jacques Cousteau. New York: G. P. Putnam’s Sons, 1976. Contains much information on the life and career of Cousteau, including his trials and victories during World War II, his development of the Aqualung, and his later explorations and endeavors. Insight is given into his personality and activities.
  • Lee, Owen S. The Complete Illustrated Guide to Snorkel and Deep Diving. Garden City, N.Y.: Doubleday, 1963. Contains a wealth of information on many aspects of diving for sport and business. Chapters 6 (diving physics and physiology) and 7 (Aqualung equipment and how it works) are most relevant. Informative and well illustrated.
  • Madsen, Axel. Cousteau: An Unauthorized Biography. New York: Beaufort, 1986. Covers many aspects of Cousteau’s experiences as a naval officer, as a coinventor of the Aqualung, and an underwater explorer. Chapter 4, on development of the Aqualung, is particularly interesting and enlightening. Useful insight into Cousteau’s personality and endeavors.
  • Parry, Zale, and Albert Tillman. Scuba America. Olga, Wash.: Whalestooth, 2001. A history of recreational scuba diving in the United States.
  • Smith, Robert W., ed. The New Science of Skin and Scuba Diving. Piscataway, N.J.: New Century, 1985. A compendium of information developed by the Council for National Cooperation in Aquatics. Designed to educate those interested in the sport and technology of skin/scuba diving. Topics covered include snorkeling, skin and scuba diving, dive planning, lifesaving, and first aid. Coverage is simple, clear, and informative.

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