The pilot reported that he was following a river, in level cruise flight at 200 feet above the water. While adjusting the engine power his attention was temporarily distracted, the airplane descended, and struck the surface of the water. After the collision, the pilot climbed the airplane to 500 feet above ground level, and proceeded directly to the nearest airport. Upon landing, the propeller, and nose of the airplane struck the ground. A postaccident inspection of the airplane revealed that the nose wheel was torn from the airplane during the collision with the water. The airplane sustained substantial damage to the engine firewall, and fuselage. The pilot stated there were no preaccident mechanical anomalies with the airplane.