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
Jacques Cousteau with the Cannes Film Festival 1951). Cousteau and the "Élie Monnier" then took part in the rescue of Professor Jacques Piccard's bathyscaphe, the FNRS-2, during the 1949 expedition to Dakar. Thanks to this rescue, the French Navy was able to reuse the sphere of the bathyscaphe to construct the FNRS-3. The adventures of this period are told in the two books "" (1953, by Cousteau and Dumas) and "Plongées sans câble" (1954, by Philippe Tailliez). In 1949, Cousteau left the French Navy. In 1950, he founded the French Oceanographic Campaigns (FOC), and leased a ship called "Calypso" from Thomas Loel