MAIB – Stena Superfast VII and Royal Navy submarine report published

Near miss between a ro-ro ferry and a submerged submarine in the North Channel between Belfast, Northern Ireland and Cairnryan, Scotland.


Statement from the Chief Inspector of Marine Accidents

On 6 November 2018, the lookout on board the ferry Stena Superfast VII spotted a submarine’s periscope close ahead. The officer of the watch then took immediate and effective action, turning the ferry to avoid a genuine risk of collision with a submerged submarine. The incident happened because the submarine’s control room team had underestimated the ferry’s speed and overestimated its range, resulting in safety-critical decisions being made based on inaccurate information.

Although there was no collision, this was the third accident or incident between a dived Royal Navy submarine and a surface vessel in 4 years, which is a matter of significant concern. The Royal Navy co-operated with the MAIB’s investigation into this near miss and has taken a series of actions, intended to prevent recurrence, in response to this, and the other similar incidents. However, I have today recommended that the Royal Navy undertakes an independent review of the actions that have been taken, in order to ensure that the risk of similar collisions has been reduced to as low as possible.


At 1256 on 6 November 2018, Stena Superfast VII’s officer of the watch took urgent action to avoid a submerged submarine after its periscope had been spotted close ahead of the ferry. Post-event analysis showed that, prior to the ferry’s course alteration, there had been a serious risk of collision. This near miss happened because the submarine’s control room team had underestimated the ferry’s speed and overestimated its range, resulting in an unsafe situation developing. However, the submarine’s control room electronic tactical display presented a picture of a safer situation than reality; this meant that safety-critical decisions made on board the submarine may have appeared rational at the time.

Safety Issues

  • safety-critical decisions need to be made based on accurate information
  • passage planning should identify all potential hazards and effective mitigations
  • maintaining a good lookout is vital for the safety of all vessels


The Royal Navy has taken a series of actions in response to this and similar previous accidents. As a result, a safety recommendation (2020/124) has been made to the Royal Navy to undertake an independent review to ensure that the actions taken have been effective in reducing the risk of further collision.

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