Who invented scuba equipment?

== == The first equipment used that actually allowed breathing underwater was invented in 1620 by Englishman Cornelius Drebbel. Designed for use in an oar-powered submarine, it used heated saltpeter to emit oxygen. The resulting potassium hydroxide absorbed the carbon dioxide produced during respiration. This first crude "rebreather" went generally undeveloped for two centuries.

Inventions in 1853 by Belgian T. Schwann, in 1878 by Englishman Henry Fleuss and in 1900 by Englishman Sir Robert Davis, were some of the earliest working self contained breathing gear. These systems were "closed-circuit" designs, meaning that the exhaled gas is retained in the system and made breathable again. They all shared the common trait of using pure oxygen as the breathing gas. This limited their use to very shallow water (<30 feet) due to the toxic effects of oxygen at increased partial pressures. These designs were primarily used, in fact, in rescue and mine safety applications until the 1930s when Italian sport spearfirshermen began to use them for spearfishing.

World War II saw the first military application of oxygen-based rebreather-type SCUBA equipment, first by the Italians using modified spearfishing units and then by the English using designs based on captured Italian units. The German firm Draeger, which had developed a rebreather for mine rescue in 1907, supplied oxygen rebreathers to the German military. All of these oxygen-based systems were limited to shallow water demolition and combat swimmer delivery. American Christian Lambertson developed this concept into the first truly modern military rebreathers beginning in 1939. Lambert's devices were the first to actually be called SCUBA, the wartime code name for self-contained underwater breathing apparatus.

As far as most divers are concerned, however, the real breakthrough in SCUBA came in in 1943 by Frenchmen Emile Gagnan and Jacques Yves Cousteau. Modifying a welding regulator into a pressure-sensitive demand regulator and coupling it with three air-filled welding gas cylinders, they invented the first open-circuit SCUBA gear. Open-circuit SCUBA allows the exhaled gas to escape into the water as waste gas. The two Frenchmen eventually sold this equpment under the name "Aqua-Lung" and started a company which became U.S. Divers and is now known as Aqualung International.

The Gagnan/Costeau invention of open-circuit (non-rebreathing) SCUBA using air as the breathing gas allowed the first widespread diving by civilians. The use of air allowed diving to depths far in excess of those allowed by pure oxygen and the open circuit design could be used safely with relatively little training. The Aqua-Lung was the key invention that opened up the oceans to generations of recreational divers.

The first Aqua-Lung designs used a single regulator mounted at the tank valve which delivered air and exhaust gases via two large-diameter corrugated over-the-shoulder breathing hoses very similar to those used by rebreathers. A generation of early SCUBA divers grew up watching actor Lloyd Bridges as Mike Nelson using double hose Aqua-Lung regulators on television's Sea Hunt program. The first modern two stage, single hose regulator was manufactured and distributed by Divers Supply in Wilmington California in the early 1950s. This design, an offshoot of surface supplied commercial gear, uses a first stage regulator mounted at the tank valve delivering air to mouthpiece-mounted second stage via a small-diameter intermediate-pressure (140 psi) hose. Today, virtually all modern open-circuit SCUBA gear uses this design, though Aqualung did market a "modern" double hose Mistral model in 2005 and 2006.