A light aircraft plunged into the Cromarty Firth after freezing temperatures caused its engine to fail.
An investigation was launched after the accident, which happened near the Black Isle last year.
Now the Air Accident Investigation Branch (AAIB) has revealed the microlight’s carburettor, which had iced during two previous descents, could have been the cause.
The 53-year-old pilot and his passenger took off Easterton Airfield, outside Elgin, on October 10, aiming to reach Invergordon via Nairn.
Investigators say the two men encountered bitingly cold air while gliding at a height of 5,500ft across the Moray Firth.
The pilot, who is believed to be from Elgin and had 125 hours of experience flying the microlight, descended to an altitude of 2,000ft to cross the Cromarty Firth, and then again to 20ft to sail over the shore.
However, when the men attempted to return the craft to its previous heights, the engine did not respond.
Faced with the prospect of crashing into rocks along the shoreline, the pilot opted to ditch the microlight into the water near Resolis, in the Black Isle.
The report says: “When the pilot attempted to apply power to climb, the engine did not respond and the aircraft descended towards the water.
“He decided to ditch the aircraft because the shore, although close by, was rocky.”
At roughly 2pm that afternoon, pilot Ivan Kinane, who was leading a flying lesson in another aircraft, spotted the microlight beneath him dropping down towards the water.
A major search was launched after he raised the alarm with Aberdeen Coastguard.
The report added that the craft “flipped inverted” as it entered the Cromarty Firth, and the men were both then able to escape the pod.
The pilot later conjectured that the loss of power may have been caused by carburettor icing during the two previous descents.
The RNLI lifeboat from Invergordon managed to recover the men, who were airlifted to Raigmore Hospital, in Inverness.
Neither man was injured during the incident, though coastguard crews described them as “shocked and hypothermic”.
The report said the upturned craft was “damaged beyond economic repair”.