In April this year, during a project mapping sunken vessels in the North Sea and Skaggerak, the Sea War Museum in Thyborøn made a sensational discovery.
Lying 123 metres down, ten nautical miles north of Skagen, was the wreck of the most advanced type of Nazi u-boat produced: a type XXI.
Of all the weapons developed by the Nazis during the Second World War, the u-boat was one of the most feared, and rightly so. U-boats were responsible for sinking about 2,779 ships, totalling around 14.1 million GRT – roughly 70 percent of all allied shipping losses in all theatres of war.
This particular boat, designated the U-3523, was depth-charged by a British Liberator bomber on 6 May 1945 – the day after Germany had officially surrendered. It was not engaged in a mission but was probably trying to escape.
The discovery was all the more surprising as the wreck was found around nine nautical miles west of the position given by the British bomber.
The type XXI boat was the first submarine designed to operate primarily submerged, rather than spending most of its time as a surface ship. It also had a much greater range than previous types and could theoretically have sailed all the way to South America in one go.
The discovered sub was one of only two that ended up in service out of 118 ordered, and neither of them took part in actual combat.
On the rocks!
After the war, Britain, France and Russia all built a number of ex-Nazi type-XXI submarines in order to study the technology.
In Russia they became known as the Whiskey-class boats and were used right up into the 1980s. One memorably ended up stranded in the Swedish skerries.
Due to the depth of the wreck, the museum has no plans to raise the submarine. Today, only one example of this type of u-boat still exists. It is at the maritime museum in Bremerhaven.