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
Philippe Tailliez hundred dives, gradually going to deeper depths. These three divers would become known as the three "mousquemers" (musketeers of the sea). The Second World War separated their team temporarily and Tailliez in particular would take part at the time of the campaign in Syria, with naval action against the Vichy navy. On armistice leave and thus having time, in 1942 they made without breathing apparatus the first French underwater film: "Par dix-huit mètres de fond" (= "18 meters deep"), and the next year "Epaves" (= "Wrecks"), this time with the Cousteau-Gagnan aqualung, and with the funds of the Marseilles company