The aircraft had a recent history of directional control problems while operating on water. On two earlier flights on the day of the accident, while landing in strong wind conditions, the aircraft had slewed sharply left when the left pontoon contacted the water. The final landing took place in light wind conditions. On this occasion, as the left pontoon entered the water, the nose of the aircraft dipped and the aircraft flipped over. Due to accident damage, it was not possible to make an accurate determination as to the cause of the control problem. However, repair work had recently been carried out on the aircraft after it struck a submerged object while landing.