The French environmentalist circled the world 15 times in his ship the "Calypso". Now it is in decay, a rusting monument to the bitter struggle for control of his name.

In the furthest corner of the old trawler harbour in La Rochelle, a ship lies half-hidden by a white tarpaulin, like a lifeless body on a mortuary slab. Streaks of rust, like blood from unseen wounds, dribble down its wooden and steel sides. Two large brown straps, resembling giant elastic bands, encircle the stern to prevent the vessel from falling apart.

If you wander up the quayside, past the Aquarium and the Maritime Museum, you have no reason to give the little ship a second glance. There is no name, no form of identification on this rotting maritime corpse. You would have no reason to know that this was once - and only a decade or so ago - the most famous small ship in the world.

This was the ship that helped to launch the modern environmental movement. This was the ship that wowed the first "colour television generation" of the 1970s with the kaleidoscopic beauty of the world beneath the waves. This was the ship which was celebrated in a mawkish hit pop song by John Denver in 1978. "Aye Calypso, the places you have been to, the things that you have shown us, the stories you tell, Aye Calypso, I sing to your spirit, the men who have served you so long and so well ... Hi dee ay-ee ooo doo-dle oh oo do do do do do doo-dle ay yee doo-dle ay ee."

The rusting hulk beneath the white tarpaulin is indeed the Calypso, the ship that circled the world 15 times under the command of Captain Jacques Cousteau, pioneer of aqualung-diving, underwater cinema and environmentalism. It is more than a decade now since the Calypso was served "so long and so well" by its famous French master and crew in the television series The Undersea World of Jacques Cousteau. In recent years, the ship has been served very badly by an endless Dickensian legal row between different branches of the Cousteau family. That row will come before the courts in Paris again tomorrow for what may be the final chapter in a wearisome tug-of-love, or perhaps rather a tug-of-hatred.

At the heart of the dispute is the bitter personal animosity between the captain s former mistress and second wife, Francine, and his son from his first marriage, Jean-Michel. Both lay claim to the spiritual, and financial, legacy of Captain Cousteau, who died in 1997, aged 87. Both lay claim to the legal title to the Calypso.

In a book published a couple of years ago, Jean-Michel Cousteau accused his stepmother, a former air hostess, of "walking off" with his father s legacy "without having any commitment to his ecological missions". Supporters of Francine Cousteau suggest that Jean-Michel, now based in California, is chiefly interested in making money from the Cousteau name through his maritime holiday resorts.

In November, after a three-year battle, the Tribunal de Grande Instance in Paris decided that the Calypso (or what remains of it) belonged to the "Equipe Cousteau", run by Cousteau s widow. That ruling will be challenged in the Cour d Appel tomorrow by an association of French divers, the Campagnes Océanographiques Françaises (COF), which represents Cousteau s son.

The Equipe Cousteau says that it has a clear legal title to the Calypso, a US-built former Royal Navy minesweeper which was originally bought for Jacques Cousteau s voyages by his friend and backer Sir Loel Guinness, of the Anglo-Irish brewing family.

After a long chapter of misfortunes, beginning with the Calypso s sinking by a barge in Singapore harbour in 1996, Mme Cousteau says she intends finally to give the ship an honourable retirement as part of an American-sponsored environmental theme park in the Caribbean. The divers association and Jean-Michel Cousteau say that, au contraire, the ship belongs to them. The proof, they say, is the Calypso s 1974 navigation certificate, issued by the French customsservice, which clearly shows that the owner is the Campagnes Océanographiques Françaises.

They say they have the support of French backers to make the Calypso a floating museum and the centrepiece of an "educational" project on the French Mediterranean coast. It would be a disgrace, they say, for a French national heirloom to be carted across the Atlantic. Besides, says Jean-Michel Cousteau, his father stipulated that he wanted the Calypso to finish its days in the Mediterranean, where he had first taken her wheel in 1951.

This assertion has been somewhat skewered in recent days by journalists on Radio France who found in the archives a tetchy soundbite from Captain Cousteau himself. "I would prefer to sink her [the Calypso] than allow her to be turned into a museum," the captain s famous gravelly voice told radio listeners in 1980. "I do not want this legendary ship to be prostituted by having people picnicking on the decks."

In truth, the legal family quarrel may already be academic. The only picnickers on the decks of the Calypso in the near future are likely - perhaps fittingly - to be fish. "Everything which is not rusted is rotten, and everything which is not rotten is rusted," lamented Albert Falco, a crew member on many of the captain s voyages (who now backs the Mediterranean museum project dear to the captain s son).

A survey on behalf of the town of La Rochelle found that the vessel was so unsound that it would have to be rebuilt, at huge cost, even to act as a floating museum. The ship was brought to the Bay of Biscay port eight years ago as part of a planned Cousteau-Captain Nemo theme park. The mayor behind the project died suddenly, and so did the theme park. (This was just one of a number of abrupt misfortunes to befall the Cousteau empire, before and since the old man s death.)

La Rochelle, fed up with having the Calypso cluttering its old trawler harbour, has offered to pay to have it towed away. But where? The most appropriate end for the Calypso, the town hall suggests, would be to tug her out to sea and let her sink as an "artificial reef" - a home for fish and a playground for divers. "It is time for the Calypso to go glug-glug," one councillor said recently.

Does the future of the Calypso matter? Is the little ship worth saving? Since Captain Cousteau s death, his reputation has suffered a series of blows, including the revelation that he held anti-Semitic views and enjoyed friendly relations during the Second World War with the Germans and the Vichy regime. There have also been allegations - confirmed by Jean-Michel - that the captain mistreated sea creatures. Cousteau s status as a triple pioneer - technical, artistic and environmental - is, however, likely to survive.

Jacques-Yves Cousteau, to give him his full name, invented the aqualung in 1943. He was the first man to shoot a full-length movie under the ocean in colour, with the help of the film director Louis Malle, in 1955. Their work - The World of Silence, mostly shot in the Red Sea from the sides of the Calypso - stands to this day as one of the greatest natural history documentaries of all time.

Cousteau s television series for the American network ABC had enormous impact in the 1970s, and the Calypso became a secondary character in the series in its own right, acting, like Cousteau s red bobble hat, as a kind of running theme. The ship was, however, for many years, the only French oceanological research vessel, engaged in scientific explorations which were in advance of anything undertaken anywhere else.

The nine-year series is Cousteau s chief legacy, all the same. The stunning films of sea-life, coupled with Cousteau s natural history lectures in romantically accented English, are now credited with helping to spawn the environmental movement.

Is there not a contradiction between Cousteau s love of nature and his occasional mistreatment of animals? In a biography of the captain published just before he died, Bernard Violet said that many "natural" scenes in early Cousteau films depended on using captured sea creatures which were goaded to perform as the script required. It was not unusual for creatures to die during filming. In his more recent book, Cousteau s son confirmed the allegations. "It is intolerable, but you have to remember that it was normal 30 or 40 years ago," he said.

Nonetheless, he insists that Jacques Cousteau was "one of the first ecologists, in the modern sense ... He was a precursor, long before others, of the concept of sustainable development." Jean-Michel also stresses (and he is not alone in this) the crucial but often neglected role of Simone Cousteau, his mother and Jacques Cousteau s first wife. Simone was the business brain behind the family enterprise, the organiser and, according to former crew members, "the real captain of the Calypso".

After her death in 1990, Jacques Cousteau married Francine, who had been his mistress for many years. Jean-Michel Cousteau broke with his father soon afterwards. In his book he says that the Cousteau project began to steer off course several years before the old man s death in 1997. "This woman [his stepmother] walked off with his legacy, without having any commitment to his ecological missions and without ever having taken part in his expeditions. For years, she has been talking of re-launching his work, without anything to show for it," he said.

Here, then, is the real source of the bitterness of the battle for control of the Calypso. The little ship has become a symbol of the legitimacy of the rival claims to represent the "true" continuing spirit of the Cousteau name. In court in Paris tomorrow, Maître Michel Dossetto, acting for the COF and, by proxy, Jean-Michel Cousteau, will make a final attempt to wrest the wheel of the Calypso from the Equipe Cousteau and the captain s widow. He will argue that the ship s 1974 certificate of sea-worthiness, issued by the French customs service, shows the owner as the COF. Under French law, such navigation certificates have always previously been accepted as absolute title to the property of a ship.

This jurisprudence was overturned in November when a lower court decided that the certificate entry was a "mistake". The judges said the paper trail showed that the Calypso had always belonged to the Guinness family and then the Equipe Cousteau. Like the biblical case tried by King Solomon, the object of all this love - and hatred - threatens to be destroyed by the argument. Looking at the Calypso today, it is difficult to believe that the little ship can be saved from joining Cousteau s undersea world. The Equipe Cousteau is favourite to win, but since the captain s death the organisation has rarely shown itself capable of carrying large projects to a conclusion.

Does anyone care? Yes, apparently, many people still do. Besides the hulk of the Calypso in La Rochelle, there stood a man in his late sixties and a boy aged about 12. Jean-Louis said that he had brought his grandson to see the ship "before it is too late". "Every week you can see that it is getting a little worse," he said. "You would not think so now, but 30 years ago, this little ship helped to open the eyes of the world." How sad. Or, in the words of John Denver: "Aye Calypso the places you have been to, the things that you have shown us, the stories you tell ... Hi dee ay-ee ooo doo-dle oh."
(The Independent, 01/03/06)