Found: Medieval Cargo Ship – Largest Vessel of Its Kind Ever

Spotted off the coast of Denmark, the “Svaelget 2” is a cog, a kind of large trading vessel used in the Middle Ages. Experts say the 600-year-old discovery is “exceptionally well-preserved”

Forty feet below the waves of Oresund, the strait between Denmark and Sweden, researchers have discovered the wreckage of a 600-year-old ship. Extravagantly outfitted and remarkably preserved, it’s a medieval cargo vessel also known as a cog. Experts say it’s the largest ship of its kind ever found.

Maritime archaeologists from Denmark’s Viking Ship Museum came across the shipwreck while surveying the seabed. According to a statement from the museum, the silt-covered vessel—called Svaelget 2—measures about 92 feet long, 30 feet wide and 20 feet tall. Experts estimate its cargo capacity was 300 tons.

“The find is a milestone for maritime archaeology,” says archaeologist Otto Uldum, the leader of the excavation, in the statement. “It is the largest cog we know of, and it gives us a unique opportunity to understand both the construction and life on board the biggest trading ships of the Middle Ages.”

Cogs were developed around the tenth century “as a safe and efficient means to transport massive quantities of goods,” writes Artnet’s Min Chen. “Their substantial cargo holds trumped [those] of Viking vessels such as knarrs, while their towering sides made them harder to board during sea skirmishes.” Per the statement, the large vessels were made to sail north from the Netherlands, around Denmark and toward the Baltic Sea. Though massive, a cog could be managed by a small crew.

“The cog revolutionized trade in northern Europe,” Uldum says. “It made it possible to transport goods on a scale never seen before.”

Uldum adds that shipbuilders made the cogs as large as possible to transport bulky cargo, like timber, bricks, salt and other food basics. No traces of cargo were found with the wreck, but researchers did uncover some of the artifacts reflecting the sailors’ daily lives, including shoes, combs and rosary beads.

The wrecked vessel is “exceptionally well preserved,” per the museum. Because the entire starboard side was buried in sand, it was protected from erosion. There, divers found lots of the ship’s rigging—the ropes and chains used to “control the sail, secure the mast and keep the cargo safe,” Uldum says. “It gives us a real opportunity to say something entirely new about how cogs were equipped for sailing.”

Svaelget 2 boasts other uniquely well-preserved structures. On its stern, researchers were shocked to find extensive remains of a castle, a kind of covered deck where the crew would have sought shelter. Records show that castles were distinctive features of medieval cogs, but no physical evidence of them had previously been identified.

“We have plenty of drawings of castles, but they have never been found because usually only the bottom of the ship survives,” Uldum says. “This time we have the archaeological proof.”

Researchers were also shocked to find remains of Svaelget 2’s brick galley, where the crew prepared food. Constructed of 200 bricks and 15 tiles, this type of fireproof galley allowed sailors to cook over an open fire. Nearby, divers found bronze cooking pots, wooden dishes, ceramic bowls and remains of meat and fish.

Dendrochronological analysis of the shipwreck’s wood revealed that Svaelget 2 was built around 1410. Its planks are made of Pomeranian oak from modern-day Poland, and the wood of its frame came from the Netherlands.

The size of Svaelget 2 is an indication of a robust trading economy in northern Europe in medieval times. It would have “required a society that could finance, build and equip these enormous ships,” as well as an adequate demand for imported cargo in faraway lands, Uldum explains.

Indeed, the centuries leading up to Svaelget 2’s construction were characterized by an agricultural boom in Europe. As Agree Ahmed wrote for Works in Progress in 2025, the continent’s population subsequently grew from 18 million in the seventh century to more than 70 million by the 14th century. The growth enabled more international trading.

“Perhaps the find does not change the story we already know about medieval trade,” Uldum says. “But it does allow us to say that it was in ships like Svaelget 2 that this trade was created. We now know, undeniably, that cogs could be this large—that the ship type could be pushed to this extreme.”