Solo diving II. In the late 1940s, after the invention of the Aqua-lung by Cousteau and Gagnan, the first retail underwater breathing apparatus for sport was commercially marketed. As the sport expanded through the 1950s, several sporting organisations – notably the Young Men's Christian Association (YMCA) – began scuba training programmes for swimming enthusiasts, thus began the codification of what was believed to be proper practices for the expanding amateur sport of scuba diving. The buddy system was thought to be a useful corollary to the "never swim alone" edicts of the YMCA swimming and lifesaving programmes. Cousteau independently implemented a buddy
Aqua-Lung order to mass-produce and sell their invention, this time under a new 1945 patent, and known as CG45 ("C" for Cousteau, "G" for Gagnan and "45" for 1945). This same CG45 regulator, produced for more than ten years and commercialized in France as of 1946, was the first to actually be called the "Aqua-Lung". In France, the terms "scaphandre autonome" ("scuba set"), "scaphandre Cousteau-Gagnan" ("Cousteau-Gagnan scuba set"), or CG45 were meaningful enough for commercialization, but to sell his invention in English-speaking countries, Cousteau needed an appealing name following English language standards. He then coined the trade name "Aqua-Lung". In the