What happened
The pilot reported that the conditions on the lake were exceptionally smooth, describing the surface as "glassy." In preparation for the landing, the pilot elected to lower the aircraft's flaps to the full extension setting. Upon initial contact with the water, the right-hand float submerged deeply into the surface. This sudden resistance caused the airplane to pitch forward violently. As the nose dropped, the right wing struck the water, leading to a loss of control that resulted in the aircraft flipping over and coming to rest upside down.
The investigation
Post-acc examination revealed no evidence of mechanical failures or malfunctions prior to the impact. The pilot confirmed that the aircraft was operating normally before the landing attempt began.
Findings
The primary factor contributing to the accident was the decision to use full flaps on glassy water. This configuration caused the right float to dig into the calm surface, initiating the forward pitch and subsequent inversion.