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
The Voyage of the Arctic Tern Rose, which was an example of a carrack warship. A bit of the Mary Rose wreck's recent history is mentioned in the story, with a brief description of its first salvage attempt in the 19th century by brothers John and Charles Deane. Other real historical figures are also briefly mentioned in the story, such as 19th century French microbiologist Louis Pasteur, and 20th century French co-developers of the Aqua-Lung, Émile Gagnan and Jacques Cousteau. The main fictional character of Bruno was inspired by a real-life diver of wrecks named Bruno, whom Montgomery had met while working on the Mary Rose