A German U-boat from the First World War is likely to have been sunk deliberately rather than being handed to the Allies, according to a 3D map produced by researchers.

The submarine UC-71 was apparently scuttled off the German archipelago of Helgoland on February 20 1919 while being transferred to the Royal Navy after the armistice.

Launched three years earlier, UC-71 sank 61 civilian ships in the North Sea using mines and torpedoes.

U-boat wreck
The wreck of UC-71 on the seabed (Prof Chris Rowland/University of Dundee/PA)

Theories abounded that it was sunk by its own crew as the hatches were open, although the official reason was bad weather and high waves.

A diary entry from an engineer read: “No Englishman should step on the boat. That was the will of the crew, and they achieved it.”

Nobody died during the sinking and the 50-metre vessel became a magnet for divers at 22 metre below sea level before it was given legal protection.

A sub-sea visualisation expert who produced the most advanced images of the wreck and used 3D maps to corroborate the theory of how it happened, branded the sinking “an act of defiance”.

Professor Chris Rowland, an expert in the 3D visualisation of underwater environments at Jordanstone College of Art and Design in Dundee, and Professor Kari Hyttinen, an expert in communication design, believe they have evidence the sub was deliberately downed.

Propellor U-boat
A close-up of UC-71’s propellor (Prof Chris Rowland/University of Dundee/PA)

During four hour-long dives, Prof Rowland and colleague Florian Huber, an underwater archaeologist with scientific diving company Submaris, took thousands of photographs.

Using state-of-the art cameras and high-intensity lighting to take stills and videos, the reconstructions were produced using a process called photogrammetry, with computers creating 3D renders using a sequence of overlapping images.

Prof Rowland said: “Hatches are certainly open across the submarine, which corroborates the claim that it was deliberately sunk.

“It is possible, however, that divers may have visited the wreck before it was protected, and highly likely that divers may even have been inside the sub, though this would be exceptionally dangerous.

“But given what we know and from the physical evidence witnessed when we were down there and from our imagery, it is likely that the boat was sunk deliberately.”

He described the process as a “walk in the park” compared with U-boats found off Orkney, due to the wreck resting on a flat seabed without too much silt.

Prof Rowland added: “This wreck is different from many others because it was sunk by an act of defiance, not an act of war.

“While the conflict may have been declared over, for those who sailed on submarines such as UC-71 there was still a tremendous loyalty to their crew, boat and nation.

“While nobody died in this sinking, UC-71 is associated with a great loss of life at sea.

“By capturing this particular wreck we are able to capture a moment in time that allows us not only to study this single act, but also serves to remind us of those who lives were claimed by the vessel during the hostilities.”

There are plans for a two-metre 3D model of the wreck to be produced using the new imagery, to sit alongside the crew member’s journal at a museum on Helgoland.