At that time, he kept his distance from his brother Pierre-Antoine Cousteau, a "pen anti-semite" who wrote the collaborationist newspaper Je suis partout (I am everywhere) and who received the death sentence in 1946. However this was later commuted to a life sentence, and Pierre-Antoine was released in 1954.<br />During the 1940s, Cousteau is credited with improving the aqua-lung design which gave birth to the open-circuit scuba technology used today. According to his first book, The Silent World: A Story of Undersea Discovery and Adventure (1953), Cousteau started diving with Fernez goggles in 1936, and in 1939 used the self contained underwater breathing apparatus invented in 1926 by Commander Yves le Prieur.Cousteau was not satisfied with the length of time he could spend underwater with the Le Prieur apparatus so he improved it to extend underwater duration by adding a demand regulator, invented in 1942 by Émile Gagnan.[8] In 1943 Cousteau tried out the first prototype aqua-lung which finally made extended underwater exploration possible.<br />Late 1940s: GERS and Élie Monnier<br />In 1946, Cousteau and Tailliez showed the film "Épaves" to Admiral Lemonnier, and the admiral gave them the responsibility of setting up the Groupement de Recherches Sous-marines (GRS) (Underwater Research Group) of the French Navy in Toulon. A little later it became the GERS (Groupe d'Études et de Recherches Sous-Marines, = Underwater Studies and Research Group), then the COMISMER ("COMmandement des Interventions Sous la MER", = "Undersea Interventions Command"), and finally more recently the CEPHISMER. In 1947, Chief Petty Officer Maurice Fargues became the first diver to die using an aqualung while attempting a new depth record with the GERS near Toulon.<br />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.
