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Aqualung was the original name for the first open-circuit free-swimming underwater breathing sets; the type most familiar at the time was the twin-hose open-circuit scuba, as developed by Emile Gagnan and Jacques-Yves Cousteau in 1943,[1] and since then made by various manufacturers with varying design details and number of cylinders. It consists of a high pressure diving cylinder and a diving regulator that supplies the diver with breathing gas at ambient pressure, via a demand valve. Before that, there were a few attempts at constant-flow compressed-air breathing sets.


Open/closed circuit

The original "Aqua-Lung" was an "open-circuit" design, so called because gas flows from the cylinder, to the diver, out into the water. Other scuba gear, invented earlier than the "Aqua-Lung", are now termed "closed circuit" or "rebreather", as gas flows from the cylinder, to the diver, through a scrubber (which removes carbon dioxide), back to a secondary bag, and back to the diver again, in a relatively closed loop; this design is commonly called a rebreather, and its old pure-oxygen form is regarded as archaic and risky when used underwater.


In the early years of scuba diving in Britain, "tadpole" as a nickname for a type of diving gear had two meanings:

  • A type of ex-RAF pilot's oxygen cylinder with a tapering end, which was often used as an aqualung cylinder in the 1960's and earlier.
  • An early make of Siebe Gorman aqualung with a twin-hose regulator and two air cylinders, with both ends hemispherical, 13 inches long and 7 inches in diameter. Siebe Gorman's trade catalog describing this set showed two sorts of diver wearing this set, both with weighted boots, and no mention of free-swimming. A 1950's Royal Navy diving manual also said that the aqualung was (only) for bottom-walking diving. Siebe Gorman had no idea then of sport diving, or was against sport diving, but expected aqualungs to be used for light commercial diving. Later, as is well known, most divers were free-swimming scuba divers; bottom-walkers became a tiny minority.

Trademark issues

Aqualung and Aqua Lung are registered trademarks for SCUBA-diving breathing equipment. That trade name is owned in the United States by the firm formerly known as U.S. Divers.

The French firm Air Liquide held the patent on the original "Aqualung" until the patent expired some time around 1960–63. The term "aqualung" as far as is known first appeared in print on page 3 of Jacques-Yves Cousteau's first book, The Silent World in 1953. Public interest in scuba diving began around 1953, in response to a National Geographical Society Magazine article in English-speaking counties, and in France a movie, and perhaps The Silent World. As with some other registered trademarks, the term "aqualung" became a genericized trademark in English-speaking countries, as a result of much use by the public and in publications including in the BSAC's official diving manuals. Presumably lawyers for Cousteau or Air Liquide could have slowed or stopped this genericization by taking prompt action, but this seems not to have been done in Britain, where Siebe Gorman had the British rights to the trade name and the patent.

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