A 1936 car accident shattered the arms of young French naval officer Jacques-Yves Cousteau, born in 1910, and ended his hopes of flying. Swimming in the Mediterranean at Toulon to recover, he borrowed a pair of Fernez goggles and became obsessed with the underwater world. During the German occupation he did covert intelligence work while filming 18 Meters Deep on held breath. In 1943 he and engineer Emile Gagnan adapted Gagnan’s gas regulator, built to feed cooking gas to car engines, into the Aqualung, whose diaphragm delivered air at the pressure of the surrounding water. Austrian diver Hans Hass later disputed who was first.

In 1950 Cousteau leased a former British minesweeper for one franc a year and made it the Calypso. His 1956 film The Silent World, made with Louis Malle, won the Palme d’Or and an Academy Award, and his 1966 series The Undersea World of Jacques Cousteau made his red cap famous. In 1960 his public campaign stopped a French plan to dump radioactive waste in the Mediterranean. His later life brought the death of his son Philippe in a 1979 flying boat crash, a 1995 lawsuit against his son Jean-Michel, a secret second family revealed in 1991, and a stark 1991 statement on overpopulation.

• From the Calypso he deduced that porpoises used natural sonar to find the deepest channel.
• The SP-350 diving saucer of 1959 carried two people to 350 meters.
• His Conshelf habitats kept aquanauts living on the seafloor for weeks through saturation diving.
• He called himself an oceanographic technician rather than a scientist.
• The invasive algae Caulerpa taxifolia is widely suspected to have escaped from the Monaco museum he directed.