Commandant Jacques-Yves Cousteau — a naval officer who became an explorer and film-maker — died of heart disease at his home in Paris on 25 June. His destiny is paradoxical. He is taken now for a scientist and a businessman, but in fact he was neither.

His reputation as a businessman arose from his talent for always finding the practical help and money needed to satisfy his all-embracing curiosity. His most famous invention, for example, came from the thought that it would be useful to have a way of being able to breathe while filming under water. He turned to the company Airliquide, where he met Emile Gagnan, an engineer who had developed a relief valve for feeding gas-fuelled engines. Together they developed a flexible relief-valve that enabled a diver to breathe compressed air from a gas bottle without choking. In 1943, following a filmed dive to a depth of 62 m, he filed a patent under the trade name Aqualung — the beginning of a great commercial success.

When, in 1950, Cousteau sought a ship with which to lead his own expeditions, he found a British benefactor, Sir Loel Guinness. With Guinness's help, he was able to buy an old mine-sweeper and convert it into an oceanographic vessel, the Calypso. Throughout his career he maintained the knack of obtaining funding for his costly expeditions, from National Geographic, the Centre National de la Recherche Scientifique, the oil companies BP and Elf, the industrial firms Fiat and Péchiney, and the American TV channels ABC and CNN.

Furthermore, Cousteau had the idea of setting up a kind of fan-club, so as to encourage donations of money from the general public. First, in 1974, he established the Cousteau Society in America and then, in 1980, La Fondation Cousteau in France. Hundreds of thousands of members, seduced by Cousteau's fight for the exploration and defence of our planet, helped him, through their subscriptions, to finance his expeditions. Cousteau knew how to find the money he needed, but he wasn't a businessman seeking to make money for himself or those around him. All the proceeds from his ventures were reinvested in exploration and film production.

Cousteau wasn't a scientist either — his training as a naval officer made him more of an engineer than a scientist. But all his life, he rubbed shoulders with science as well as technology. To be able to film underwater, he had to continually invent: an autonomous diving system (the aqualung), waterproof cameras, underwater lighting, ‘diving saucers’ (able to dive and move about on the sea bottom), sea-scooters.... Knowing what he wanted, knowing whose doors to knock on, he always found the people and equipment he needed to realize his technical feats. In this way, he brought in a new era of underwater diving.

In organizing expeditions for scientists, he also provided a shot in the arm for oceanography, which had been advancing in fits and starts since the initiatives of Prince Albert the First of Monaco at the beginning of the century. By inviting a wide range of scientists — geologists, marine biologists, botanists, zoologists, archaeologists and biochemists — on board the Calypso, one might even venture that he invented marine field ecology, enabling a cross-fertilization of ideas, approaches and findings.

When, in 1966, the French government launched its own oceanographic vessel, the Jean-Charcot, Cousteau devoted himself exclusively to producing films for television. From that time on, the scientists invited on board Calypso were doing no more than fitting in with the needs of the film crews. When exploring the great rivers of the world (St Lawrence, Mississippi, Nile, Amazon, Danube), the researchers served, above all, as a guarantee to local authorities that no monkey business was afoot. And because representatives of national universities were on board, the authorities allowed access to inhospitable or forbidden regions. In exchange, Cousteau made available to the host country all the results of his team's research. Most important of all, for Cousteau, was to bring back films for the general public.

This shift from research to cinema provoked the deepest distrust within the scientific community. All the more so because Cousteau had let it be written everywhere — including in his own publications — that he was a great scholar. Of course, one can be a great connoisseur of the oceans and sea floor without being the slightest bit scientific. But for Cousteau, science was not confined to the laboratory and the literature. To explore the unknown was, for him, the very essence of the scientific process. To discover a wreck, to explore an underwater cave, to encounter a new species of fish was, for him, a scientific work. Especially if, rather than keeping the discovery secret, it was broadcast to the world's television and cinema screens; and even if, in the haste of so doing, it meant making mistakes or approximations.

In his last work L'homme, la Pieuvre et L'orchidée (Man, the Octopus and the Orchid), published the day after his death, Cousteau admits that he had had only “brief encounters with science”. But he can't find words harsh enough to denounce military and industrial secrecy in fundamental research. “All those who maintain secrecy over discoveries that might affect human health and life, they are nothing less than criminals”, he writes, claiming to have published all his findings on the physiology of diving because he valued a diver's health above manufacturers' secrets.

This popularization is not much appreciated by the research fraternity. Their displeasure is greatest when the popularization is by way of mass-appeal television programmes, where one sees more of the man, Cousteau, and his divers, than the science. But Cousteau himself was emphatic about his approach, even if it later meant making U-turns, as he did in eventually criticizing the discharges of bauxite into the sea by Péchiney and the French nuclear tests at Mururoa, and in recognizing that the supposed ‘death’ of the Mediterranean Sea had failed to happen.

The fact remains that Cousteau, through his technological innovations, gave a healthy lift to oceanography after the Second World War. With his films, he has also aroused the curiosity of millions of television viewers, and shown, using pictures, how our planet is both rich and fragile. As for science with a big ‘S’, he says this in his posthumous work: “We have succeeded in using science to conquer nature. We could surely use it to conquer human nature.” And, presumably, make humankind less destructive.