RC Extra EA-300 splashdown crash: Flight Five

The extra 300 RC plane is powered by a 2 bladed 10 x 5 APC propeller. When powered by the 2000mah 4S. It pulls 30 amps at full throttle, producing 1.5kg of thrust.
The model is an original build from plywood, balsa, and fibreglass.
Flight Review:
The flight started off well until mid way through disaster. The receiver stopped communicating with the transmitter, and I watched the plane slip lower and lower until I lost sight. The only thing I could see from the flight line was the splash. It continued to float until I managed to retrieve it. Go Pro still running and attached with wet masking tape.