The solo airline transport certificated pilot was landing a float-equipped airplane in a remote, freshwater bay. The pilot reported that during the landing roll, he added a slight amount of left rudder to straighten the airplane's track on the water. The airplane subsequently cart-wheeled to the left, nosed over, and sank in shallow water. The airplane sustained substantial damage to the wings, fuselage, and empennage. The pilot reported that there were no preaccident mechanical anomalies with the airplane.