What happened
A private pilot was attempting to land a Cessna float-equipped airplane on choppy water during a 10-knot left-quartering headwind. The aircraft made a hard impact on the left float, bounced into the air, and subsequently landed on the right float. This caused the right wing to contact the water, resulting in a nose-over maneuver. The aircraft came to rest with the left wing submerged and the right wing pointing upward.
The three passengers on board successfully released their seatbelts and exited through the right cabin door. However, both the pilot and the passenger in the right-front seat were unable to locate, release, or cut the pilot's seatbelt. As the aircraft slowly rolled into an inverted position, it remained afloat. Passengers and a rescuer from the shore attempted to open the pilot's locked door but were unsuccessful, and they could not remain submerged in the 40-degree Fahrenheit water. A diver eventually reached the pilot; once the seatbelt was released, the pilot was removed without difficulty.
The investigation
Post-accident inspection by the Investigator-in-Charge (IIC) determined that the door functioned normally once unlocked. However, accessing the pilot's door handle required the occupant to twist their torso to the left and reach behind their shoulder. The seatbelt buckle, which could be opened with one hand using less than 10 pounds of force, was positioned aft of the pilot's left hip, sandwiched between the seat and the left door. When the door is closed, the buckle is masked under the door armrest.
The Cessna inertial reel, seatbelt/shoulder harness assembly was found to be installed according to manufacturer specifications.
Toxicology tests performed on the pilot revealed the presence of phentermine, a prescription stimulant, in his blood and urine. No record of a prescription for this medication was found.