What happened
A certificated flight instructor was conducting flight instruction and recurrent training for a second pilot, who held a commercial pilot certificate. Prior to the accident, the crew had successfully completed two landings on the same sand bar.
During the final approach to the south, the second pilot was manipulating the controls when the aircraft encountered a downduring. This caused the airplane to land in a river just short of the intended touchdown point. The aircraft came to rest upside down in approximately three feet of water. Both pilots were not injured.
At the time of the accident, the wind was reported as being from 180 degrees at 10 knots.