After half a century of service, first as a minesweeper during the war, then as the Gozo ferry boat and most famously as Jacques Cousteau's research vessel for 46 years, the Calypso is now being restored at a French shipyard.

Thanks to the late Captain Jacques Cousteau's films and television documentary series The Silent World and the Undersea World of Jacques Cousteau, which have been seen universally, the nautical research ship Calypso has been turned into one of the most famously filmed and well-known vessel in the world.

Prior to Capt Cousteau's acquisition in 1950 when she was found in a Malta dockyard for surplus ships, she had been a World War II minesweeper operating with the 153rd Minesweeping Flotilla.

Built in Seattle, she was launched on March 21, 1942 at the Ballard Marine Railway Yard by Isobel Prentice, the schoolgirl daughter of the shipyard's foreman. Calypso was part of the American Lend-Lease scheme, an agreement struck between the United Kingdom and America whereby the latter provided the former with ships, planes and shells for the duration of the war on a "never-never" basis.

These little ships were known as British Yard Minesweepers (BYMs) and were identified only by their numbers. They were crewed by 30 officers and men, who performed dangerous tasks, worked hard and were very courageous, clearing the seas of mines in all kinds of weather. In performing these unenviable duties they were simultaneously subjected to aerial and torpedo attacks. A total of 130 were built for the Royal Navy to an Admiralty design and they quickly proved their worth, sweeping 500 mines in three months. Only six were lost during their war service, all by mine explosion.

British Yard Minesweepers all sailed with the pennant J. Calypso was commissioned as HMS J-026 and in February 1943 she sailed from Seattle bound for Gibraltar via San Francisco and Freetown - a voyage of 16,000 miles. En route she suffered a breakdown and had to put into San Diego for repairs. Later that year she joined up as a unit of the 153rd Minesweeping Flotilla in the Mediterranean Fleet based at Malta. She took part in the initial assault convoy to the beaches of Sicily in Operation Husky escorting and supporting the vast Allied invasion, sweeping close to the beaches to enable the landing craft to move in. These Allied landings marked the turn of the tide of the war in the Mediterranean and elsewhere.

In 1944 she was renumbered BYMS 2026 and based in Taranto, Italy. She was decommissioned in 1946 and laid up in Malta where she was acquired by Joseph Gasan, a Maltese businessman who used her commercially for a short period as a car ferry which operated between Malta and Gozo in the 1950s. In this configuration she was capable of carrying 11 cars and 400 passengers, and her name was changed to Calypso G.

Homer's Odyssey tells us that Calypso was a nymph who held Ulysses prisoner of her charms for seven years when he was shipwrecked on the island of Ogygia, better known nowadays as Gozo.

Captain Cousteau had long dreamed of devoting his life to exploring the mysteries of the Ocean World. This became possible when the French Navy transferred him to the Naval Reserve to allow him to conduct research on diving and underwater exploration. He found his ideal ship, Calypso - a vessel which had all the qualities for which he had been searching. Constructed of wood so as not to attract magnetic mines and also because of the possibility of having to withstand the occasional underwater explosion, minesweepers were built with a double hull - Calypso's was in excellent condition and she was sturdy. She had twin engines, was easy to handle and had a shallow draught, which would permit access to areas such as coral reefs.

In July, 1950, renamed Calypso she was taken to a shipyard in Antibes where she was converted from ferryboat to Oceanographic Research Vessel. Naturally, this entailed extensive alterations to turn her into a floating laboratory. Navigational aids were added, as were special facilities for diving equipment. An underwater observation chamber known as Calypso's false nose was also installed. It was connected to a metal well built around the stem, which extended eight feet below the waterline. This chamber enabled two crew members to film and observe underwater without leaving the ship.

In 1969, as Calypso was leaving the Galapagos, she struck an uncharted rock, which damaged her false nose as well her keel. The false nose was rebuilt and the keel repaired later in New Orleans.

Sadly, on January 8, 1996 after a barge struck her and punctured her hull below the waterline, Calypso sank and lay at an angle of 70° in five metres of water at Singapore Harbour. At the time she was awaiting her next expedition although Captain Cousteau was preparing to retire her. She was salvaged on January 25, 1996 and then retired to Marseille after 46 years' service with Capt Cousteau. Her two shaft diesel engines, which gave 1,200 bhp and had powered this vessel since 1942 had been replaced in 1986 after 40 years in commission.

After her return to France, owing to a dispute over her future, she lay rusting away at the French port of La Rochelle, her future uncertain.

All the legal battles are now over and Calypso, having been abandoned at La Rochelle for the past 10 years, is now being completely refitted at Concarneau. The refit is expected to take 18 months and has been entrusted to the Finisterienne de Construction et Reparation Navale company. They claim that it will be almost a brand new Calypso which will eventually emerge from their yard and go to sea once more.

It had been Captain Cousteau's wish that Calypso would be restored to her former glory and end her days in the Mediterranean where he first clasped her wheel in 1951.