The commanding officer of a Royal Navy submarine that ran aground off the Isle of Skye failed to "appreciate the proximity of danger", lacked charts and was uncomfortable navigating in the dark, according to the findings of an official inquiry.
The £1bn HMS Astute was on a test mission when it became stuck in a shingle bank near Skye on 22 October 2010 and ended up marooned for several hours.
Equipped with cruise missiles and torpedoes, Astute is the first of three nuclear submarines capable of spending unlimited periods at sea with a capacity to carry 109 crew.
Its crews are considered among the most elite in the Royal Navy but the report found that "lack of early communication" with its base, MV Omagh, contributed to the grounding.
Rear Admiral Ian Corder, head of the submarine service, said he accepted all the findings, and said: "Remedial actions have either been completed or are under way." He added that he would not say who had been reprimanded because "this is a private matter between those concerned and the naval service".