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
Recreational diving owners of the Cousteau and Gagnan designed twin-hose scuba. The first school to teach single hose scuba was started in 1953, in Melbourne, Australia, at the Melbourne City Baths. RAN Commander Batterham organized the school to assist the inventor of the single hose regulator, Ted Eldred. However, neither of these schools was international in nature. There were no formal training courses available to civilians who bought the early scuba equipment. Some of the first training started in 1952 at the Scripps Institution of Oceanography where Andy Rechnitzer, Bob Dill and Connie Limbaugh taught the first scuba courses in the United