The pilot flew the ski equipped aircraft to a frozen lake where he met two friends who were ice fishing. Later, after he visited with his friends and had given each of them a ride in the aircraft, the pilot took off again. After takeoff, the pilot turned back at low altitude and flew over the vicinity of his friends. Other fishermen saw the pilot wave as he flew by. Several witnesses reported that the pilot was at or below tree level as he flew back over the frozen lake. He was observed to turn toward tall trees at the shoreline, then pull up as if to climb over the trees. Suddenly, the nose dropped and the plane impacted on the ice. The witnesses reported that the engine seemed to operate normally until impact. A canvas pouch with marijuana, hashish, and cocaine was found in the pilot's coat pocket. A toxicological test of the pilot's blood revealed .042 per cent alcohol but no drugs. This test would not have identified marijuana.