HMS Wasa (also Vasa) is a famous ship built for the Swedish Monarch Gustavus Adolphus of the House of Vasa, between the years 1626 and 1628. The ship's construction was plagued by interference from the King. Shortly after the keel had been laid the king insisted that it be lengthened significantly. The master shipwright who had been overseeing the construction became ill and died leaving his inexperienced apprentice in charge of construction.

The king then insisted on the addition of a second gun deck. The resulting vessel was the best equipped and most heavily armed warship of its day, but one that was too long and tall for its width. The standard stability test of the day was thirty sailors running from side to side trying to rock the boat. When this was attempted on the Vasa the ship tilted significantly and the test was canceled. As none dared inform the king, the ship readied for launch.

On August 10, 1628 the Vasa set sail on her maiden voyage to the harbor of Stockholm. In the harbor a gust of wind forced the ship on her portside, after which water started flowing in through her open gun ports, and she soon sank killing about 50 sailors.

Anders Franzén thought of the possibility of recovering wrecks from the Baltic waters, because he figured that these waters were free from the shipworm Teredo navalis. He started looking for the Vasa, and found her in an upright position at a depth of 32 meters. The wreck was lifted in a relatively straightforward way, by digging six tunnels under the hull, through which steel cables were to be attached to a lifting pontoon. The ship was lifted and brought to shallower water, where she was to be made watertight for the final lift. Her gun ports were closed by means of temporary lids, and all the holes from the iron bolts, which had all rusted away, were plugged. The final lift took place on April 24, 1961, after which she was put in a dry dock.

Conservation of the ship itself was done using polyethylene glycol, a method that was also used years later in the conservation process of the Mary Rose. The Vasa was sprayed with this glycol during 17 years, followed by slowly drying. Recent developments have shown that this conservation method, in time, makes the wood brittle and fragile.

Over 26,000 artifacts have been found, including six original sails, still folded up. After the lifting of the wreck, the wreck site was searched for artifacts and over 700 sculptures were found. These sculptures were once attached to the ship, but the bolts had rusted away, causing the sculptures to fall to the bottom.

The ship can be seen in the Vasa museum in Stockholm, Sweden.

See also: Maritime archeology, Royal Swedish Navy