The submarine, which was deliberately sunk in 1918, was used to boost Britain’s defensive power in the war.
The protected status of the wreck, off the coast of Dartmouth, Devon, means it can be dived, but its contents are protected by law and must not be moved.
A team of specialist divers found the submarine during an investigation and reported the find to Historic England.
Lead diver Steve Mortimer, who was part of the team searching for the remains of German U-boats when they came across the wreck, said: “Every diver dreams of identifying a historically important wreck.”
