HMS Superb was submerged on a training exercise when it ran head-on into rocks, seriously damaging its sonar equipment.
A source revealed the terrified crew thought they had hit the ocean bed.
He said: "The vessel was at such a depth that when it hit, those on board thought they had hit the bottom of the ocean. There would have been a significant impact but the emergency procedures were quickly put into place.
"The crew were shaken but none are injured. With a nuclear reactor on board there are real fears for the stability of the vessel and the safety of those on board but tests showed everything was ok."
The 272-ft vessel was around 80 miles south of
Kate Hudson of the Campaign for Nuclear Disarmament said: "This is yet another submarine crash. It must set alarm bells ringing at the MoD. As a result, what we have is like a floating nuclear power station, surrounded by high-explosives in the most sensitive region of the world."..MIRROR