A nearly 800-year-old medieval merchant ship, or cog, has been found in the Fjällbacka Archipelago in Bohuslän County, Sweden.
The wreck, about ten metres long and five metres wide, was located on a muddy bottom in a shallow bay not far from summer guests' boathouses and was found more or less by chance by a team of Gothenburg University archaeologists with a group of freelance colleagues. The crew had information about another wreck, from the 17th century, but found something better instead.
According to marine archaeologist Staffan von Arbin, only a dozen wrecks from the 13th century have been found in Swedish waters so far. This one is not only the oldest in Bohuslän County, but one of the oldest in all of Europe, the newspaper Dagens Nyheter reported.
Von Arbin added that the ship had likely caught fire before it sank, as charred coal was found inside. Whether it was an accident or a hostile act remains unknown. A pirate attack to gain access to the goods on board has not been ruled out.
The original cog could have been up to 20 metres long. Given that the condition of the ship is even more remarkable, after centuries in water. By analysing wood from the wreck, dendrochronologist Aoife Daly of the Saxo Institute, Copenhagen, was able to establish that it was built of oaks felled between 1233 and 1240.
The analysis showed not only the age of the wood, but also the place of origin. The cog is built of trees from northwestern Germany and thus has been tied to the powerful Hanseatic League, which accounted for a large share of trade in medieval northern Europe.
During the Middle Ages, Bohuslän was part of Norway and along its coast lay important trade routes served by the ships going from the Baltic Sea to the British Isles or down to the continent.
Medieval sailors had neither maps nor compasses and had to rely entirely on their own knowledge or on local pilots. They followed the coast for as long as possible and avoided sailing at night. When darkness came, the sailors sought refuge in local harbours or sheltered bays like the one in Fjällbacka.
Cogs first appeared in the 10th century, but were widely used from around the 12th century onwards for their capacity to carry goods. Cogs were clinker-built, generally of oak, and fitted with a single mast and a square-rigged single sail. A typical cog was between 15 to 25 metres in length.
According to Staffan von Arbin, more dives may be required for a comprehensive investigation.