A watchkeeper may have been distracted by using his tablet computer before a collision between two ships at sea, an inquiry has found.

The cargo ship Daroja and oil bunker barge Erin Wood collided off Peterhead on August 29 last year, putting the lives of two crewmen in grave danger

The Erin Wood heeled over 90 degrees and water rushed in. The deckhand, who was in the mess room, was fully submerged in seawater while the skipper escaped from the flooded bridge through an open window.

The Cyprus registered Daroja sustained minor damage, but damage to the St Kitts and Nevis registered barge included breaches of the hull, resulting in flooding of the vessel and pollution from leaking fuel cargo.

A Marine Accident Investigation Branch (MAIB) report into the incident, which happened four nautical miles south east of Peterhead, found that poor watchkeeping by lone watchkeepers led to the collision.

At the time of the incident, both vessels were manned by watchkeepers who were not keeping a lookout and were therefore unaware of the risk of collision.

On board Daroja the chief officer, who was the officer of the watch, missed opportunities to detect Erin Wood by visual, radar and automatic identification system means, according to the report.

This happened because he had become "complacent through distraction, inattentiveness, the repetitive nature of the vessel's schedule and insufficient supervision", it said, stating that he became distracted "primarily by cargo paperwork but also by a phone call and, potentially, the use of his tablet computer".

On board Erin Wood, the bridge was not continuously manned and, although the skipper was aware of the presence of another vessel, the situation was not effectively assessed and an assumption was made that a larger ship would keep clear.

No-one was injured but the report found that the flooding placed the Erin Wood and the lives of both crewmembers in grave danger.

The investigation also identified "significant safety shortcomings" in the management and operation of Erin Wood.

MAIB said that safety recommendations were made to the managing companies of both vessels which were intended to improve standards of navigation and watchkeeping.