What happened
A check pilot and another company pilot, who was undergoing initial operating experience, were preparing for a positioning flight following the transport of a passenger. The crew elected to perform a back taxi within the bay to facilitate a takeoff into the wind.
After the second pilot completed the back taxi and a right-hand turn, the check pilot took control of the unspecified aircraft to instruct the other pilot on performing downwind turns to the left. During this maneuver, while the airplane was pointed into the wind with the engine power at idle RPM, the aircraft simultaneously rolled and nosed over onto its left float.
At the time of the event, weather conditions were characterized by winds from 330 degrees at 20 knots, gusting to 25 knots. The water surface was described as choppy, with white water visible on the tops of the waves.