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
Aqua Lung/La Spirotechnique coined by Cousteau himself on that purpose. In the USA during World War II the American military physician Christian J. Lambertsen designed a wartime frogman's rebreather which in 1952 got called the SCUBA (acronym for Self-Contained Underwater Breathing Apparatus), and later the name (changing to 'scuba' and treated as a word) was used to mean any underwater breathing set. In Britain the word "aqualung" became a generic trademark for open-circuit underwater breathing sets and stayed so for many years. The word "scuba" became the generic word quickly in the USA and eventually in Britain. For more information see Aqua-lung#Trademark issues.