A medieval ship has been raised after half a millenium of resting on a riverbed in The Netherlands.

Archaeologists have confirmed that the find is a 15th century "cog" - a trading vessel used to sail the North and Baltic Seas, according to Sky News.

While evacuating the port of the city of Kampen, construction workers came across the skeleton of the ship underwater beneath sand and silt.

It measures approximately 20 metres by eight, weighs about 40 tonnes, and is believed to have lain there for about 500 years.

The ship as it first appeared before being excavated (YouTube, Ukraine Today)

Archaelogist Wouter Waldus said after the ship had been weighed they knew the structure was stable. It even has a brick-arched oven and glazed tiles intact on the rear deck, according to Sky News.

Because of metal joints across the structure, it was sturdier than other vessels of the same era and was remarkably well-preserved, said experts.

Named "Ijsselkogge" after the river delta it was found in, the structure was brought out of the water in a specially constructed metal frame, with straps around it controlled by a computer.

A metal frame was placed around the boat to remove it in one piece from the river (YouTube, Ukraine Today)

A cog was a type of ship generally built of oak, fitted with a single mast and a square-rigged single sail, which first appeared in the 10th century and was widely used from around the 12th century in medieval Europe.

They were particularly used by the Hanseatic League, which was a commercial and defensive network of ties between merchant guilds across the Baltic and North sea.