Modern scuba gear consists of one or more gas tanks strapped to the diver's back, connected to an air hose and an invention called the demand regulator. The demand regulator controls the flow of air, so that the air pressure within the diver's lungs equals the pressure of the water. Emile Gagnan and Jacques Cousteau invented the demand regulator and the autonomous diving suit.
Divers probably began using snorkels made of hollow reeds about
100 A.D. as the first piece of diving equipment.
By 1300, Persian divers were using underwater eye-goggles, made from the polished shells or tortoises. In the 16th century, barrels were used as primitive diving bells, and for the first time divers could travel underwater with more than one breath of air, but not much more than one.
In 1771, British engineer, John Smeaton invented the air pump. A hose was connected between the air pump and the diving 'barrel', allowing for air to be pumped to the diver.
In 1772, Frenchmen, Sieur Freminet invented a 'rebreathing' device that recycled the exhaled air from inside of the barrel -- this was the first self-contained air device. Freminet's invention was a poor one; the inventor died from lack of oxygen after being in his own device for twenty minutes.
In 1825, English inventor, William James designed another self-contained breather -- a cylindrical iron "belt" attached to a copper helmet. The belt held about 450psi of air, enough for a seven minute dive.
In 1876, Englishmen, Henry Fleuss invented a closed-circuit, oxygen rebreather. His invention was originally intended to be used in a repair of an iron door of a flooded ship's chamber. Fleuss then decided to use his invention for a thirty foot deep, dive underwater. He died from the pure oxygen; oxygen is toxic to humans under pressure.
In 1926, French naval officer, Yves Leprieur invented a system using a 2,000-psi steel tank, which flowed air into a full-face mask.
In 1939, American, Dr. Christian Lambertsen designed a 'Self-Contained Underwater Oxygen Breathing Apparatus' for the U.S. military. It was part of the war effort, code-named 'SCUBA'. Lambertsen's 'SCUBA' gear worked for shallow dives, but the gas mixture was wrong for greater depths and divers were dying from the oxygen toxicity.
In 1943, Frenchmen, Emile Gagnan and Jacques Cousteau invented the demand regulator, which adjusted the air pressure automatically, supplying air as the diver needed it. Gagnan had started design work on a similar regulator for automobile research, when cooking oil was used to replace gasoline during the war. Gagnan designed a New Products regulator to work with the cooking oil fuel.
Together, Gagnan and Cousteau further improved the designs of diving equipment. Their regulator was connected to three cylinders, each holding 2,500 psi of air. The complete equipment, or autonomous diving suit with the pressure regulator, was called the "Aqua-lung".
The "Aqua-lung" is the basis for modern equipment used today, most historians refer to Gagnan and Cousteau as the fathers of modern scuba diving gear.