August 10, 1628, was a great day for Stockholm. The city filled with patriotic, excited crowds as news spread that Vasa, the mighty man-o'-war named after the Swedish royal family, was to sail at last.

      King Gustavus Adolphus himself had masterminded her design. Intended to carry 300 fighting men as well as a working crew of 133, she displaced about 1400 tons. Forty acres of timber had gone unto her construction.

      Her topgallant soared to 164 ft, and 64 bronze cannon were mounted on her three decks.

      Now the great warship was ready for the sea. It was 4 o'clock in the afternoon: to the cheers of the crowds on the shore and the thunder of the fleet's gun fired in salute, Vasa weighed anchor and slid gracefully away.

      Then came disaster, sudden, startling and total. A squall blew up in the bay and the ship listed to port. Before the crew could haul the guns to redistribute the weight, water was pouring in through the square, open gunports of the lowest deck. In minutes, the sea closed over Vasa. There were few survivors.

Discovery under the sea

      It was not until almost 300 years after the lost of the ship that two clues, which at first seemed insignificant, led a determined young man to pull off one of the most spectacular coups in the history of underwater exploration.

      The first clue was teredo navalis, or shipworm, a destructive 1 ft long mollusk, which was plagued wooden ships since man first ventured to sea.

      Cruising off the west coast of Sweden in the late 1930s, Anders Franzen, who was then just 20, came across some flotsam riddled with teredo worm. This seemed odd to Franzen who, accustomed to sailing in te Baltic, had never before seen timber so badly worm-eaten.

      He investigated, and learnt that the Baltic is not sufficiently salty for the teredo worm to flourish. So he reasoned that the Vasa, which had sunk in Baltic waters, might still be intact.

      After the war, Franzen, who had dreamt of salvaging an old ship, gleaned every scrap of information available about the Vasa and the place where she had sunk. He swept the harbour floor with grapnels and drag-wires--bringing up nothing but old bedsteads and all manner of junk. For four years his prize eluded him. But all the time he was getting closer.

Oak turned black

      Then the second clue that was to guide him to his goal fell into his hands. Sounding the harbour floor one day in 1956, his core-sampler--a device for picking up samples of the sea-bed--struck something solid. He raised the line and brought up a piece of ancient black oak. Franzen knew that in these waters it took at least 100 years for the oak to turn black, so he must have stumbled upon an old ship. Could it be Vasa?

      Franzen's hunch was confirmed by naval divers, who found Vasa 110 ft down, wedged up to her original waterline in 16 ft of mud.

      The first stage in the salvage operation was to pass steel cables under the ship, suspended from pontoons, and then, by raising and lowering the pontoons, 'bounce' the hulk free and into shallower water. This took two years.

      Next, divers closed all the gunports, plugged every possible leak, and finally brought her up on April 24, 1961, with cables, inflatable pontoons and a system of hydraulic jacks.

      Today, the Vasa rests in a specially built museum in Stockholm. She is continuously sprayed with steam and special chemicals to stop her timbers warping and shrinking to destruction.

      Her resurrection was a triumph of underwater discovery and salvage; an achievement for which history will award some part of the credit to a destructive little creature called the shipworm.