Discovery of rare medieval wreck, believed to be Sweden's oldest warship

Bubbles rise to the surface of murky green water off the coast of Stockholm as underwater archaeologists carefully study a rare 15th-century wreck, the oldest warship discovered in Sweden. “It's a very large ship, it was probably between 40 and 45 meters when it was sailing,” notes Håkan Altrock, project manager at the Swedish Shipwreck Museum.

On this cold October day, he supervises the dives towards the remains of the hull of the ship, nicknamed Vrak 5 (wreck number 5). Located near Häringe Castle, south of Stockholm, this wreck is that of the oldest warship discovered off the coast of Sweden or Denmark, two kingdoms which formed a union with Norway in the 15th century. Discovered at the end of the 19th century, this relic rests at the bottom of the Landfjärden Strait, alongside four other sunken ships, most of which date from the 17th and 18th centuries.

In February 2025, researchers managed to date Vrak 5 to the 1480s, or even 1460. “It is impossible to say whether it is a Swedish ship, it could just as easily be Danish,” says Håkan Altrock. “This is the first known example, in the Baltic Sea, of a ship built using the freeboard planking technique” in Scandinavia, he explains. This shipbuilding technique involves assembling the hull planks edge to edge, rather than overlapping them. It made it possible to build larger and more robust ships, a necessary development with the appearance of heavy guns on board ships.

This week, underwater archaeologists began excavations to better study the ship, particularly to learn more about the crew's diet. They used special pumps to suck up the sediment to bring out certain parts of the ship's structure.