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
Jacques Cousteau an aqualung, while attempting a new depth record with the GERS near Toulon. In 1948, between missions of mine clearance, underwater exploration and technological and physiological tests, Cousteau undertook a first campaign in the Mediterranean on board the sloop "Élie Monnier", with Philippe Tailliez, Frédéric Dumas, Jean Alinat and the scenario writer Marcel Ichac. The small team also undertook the exploration of the Roman wreck of Mahdia (Tunisia). It was the first underwater archaeology operation using autonomous diving, opening the way for scientific underwater archaeology. Cousteau and Marcel Ichac brought back from there the Carnets diving film (presented and preceded