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 with whom he had two sons, Jean-Michel (born 1938) and Philippe (1940–1979). His sons took part in the adventures of the "Calypso". In 1991, one year after his wife Simone's death from cancer, he married Francine Triplet. They already had a daughter Diane Cousteau (born 1980) and a son, Pierre-Yves Cousteau (born 1982), born during Cousteau's marriage to his first wife. The years of World War II were decisive for the history of diving. After the armistice of 1940, the family of Simone and Jacques-Yves Cousteau took refuge in Megève, where he became a friend of the Ichac family who