Buddy diving just before and after the Second World War. After the invention of the "aqualung" by Cousteau and Gagnan, the first commercially underwater breathing apparatus became available for sale for sporting purposes in the late 1940s. As the new sport of scuba diving rapidly expanded through the 1950s, several sporting organisations—notably the YMCA—began programmes to train swimming enthusiasts in this new aquatic pastime, and began to codify what they believed were proper practises for this expanding sport. The YMCA considered the buddy system a useful corollary to the "never swim alone" rule of their swimming and lifesaving programmes. Cousteau himself independently
History of underwater diving develop the single-hose open-circuit scuba system, which separates the first and second stages by a low-pressure hose, and releases exhaled gas at the second stage. This avoided the Cousteau-Gagnan patent, which protected the twin-hose scuba regulator. In the process, Eldred also improved performance of the regulator. Eldred sold the first Porpoise Model CA single hose scuba early in 1952. In 1957, Eduard Admetlla i Lázaro used a version made by Nemrod to descend to a record depth of . Early scuba sets were usually provided with a plain harness of shoulder straps and waist belt. The waist belt buckles were