Scuba set

In June 1943, Jacques Cousteau took his first real dive with a new apparatus in the Mediterranean Sea near Bandol, France. Strapped to his back were compressed air cylinders; in his mouth, a mouthpiece connected to a demand regulator that delivered air only when he inhaled. No hoses to the surface. No heavy helmet. No need for surface tenders. For the first time, a human could swim freely underwater, breathing as naturally as walking on land. The Aqua-Lung—later generically known as scuba (Self-Contained Underwater Breathing Apparatus)—had arrived.

The invention emerged from an unlikely wartime collaboration. Cousteau, a French naval lieutenant with a passion for underwater exploration, had spent years frustrated by the limitations of existing diving equipment. Surface-supplied helmet diving was cumbersome, tethered, and limited. Oxygen rebreathers worked but were dangerous—pure oxygen becomes toxic below about 20 feet. What Cousteau needed was a demand regulator that would supply compressed air at ambient pressure only when the diver breathed in.

The connection came through Cousteau's wife Simone. Her father was an executive at Air Liquide, France's largest compressed gas company. In late December 1942, during the German occupation, she asked if anyone at the company understood demand regulators. Her father knew Émile Gagnan, an engineer who had designed a demand valve for converting automobiles to run on cooking gas—an adaptation necessary when the Nazis commandeered all gasoline. The same principle that metered fuel when a driver pressed the accelerator could meter air when a diver inhaled.

Gagnan adapted his automotive regulator for underwater use within weeks. Initial tests in a frigid Parisian river revealed a problem: the device worked while horizontal but leaked air when vertical. The solution was elegant—relocating the intake and exhaust tubes to the same level eliminated the pressure differential. Over the following months, Cousteau, his friend Frédéric Dumas, and Philippe Tailliez made over 500 test dives, cautiously pushing deeper. By autumn 1943, they had reached 130 feet; by October, Dumas had descended to 210 feet.

The Aqua-Lung solved the critical problem of wasted air that had limited previous self-contained apparatus. Earlier designs either continuously released air (quickly exhausting supply) or used pure oxygen (toxic at depth). Gagnan's demand regulator released precisely the amount of air the diver needed at exactly the pressure required for that depth—nothing wasted, nothing toxic.

Commercial production began in France in 1946. By 1951, the system was sold in England and Canada; US distribution began in 1952 through US Divers. The invention transformed underwater exploration from a specialized industrial and military activity into something anyone could learn. Marine biology, underwater archaeology, recreational diving—entire fields emerged or expanded dramatically. In the 79 years since Cousteau and Gagnan's invention, over 28 million people have learned to scuba dive, exploring a realm that had been accessible only to a handful of helmet divers. The ocean, covering 70% of Earth's surface, became a place humans could actually visit.