On June 29, 2005, about 0845 Pacific daylight time, a Cessna 180A, N2929C, impacted water during a landing approach to an unimproved area at the Iron Canyon Reservoir, 4 miles northwest of Big Bend, California. The pilot-owner was operating the airplane under the provisions of 14 CFR Part 91. The commercial pilot, the sole occupant, sustained minor injuries; the airplane was substantially damaged. The personal cross-country flight departed Paradise, California, about 0800, en route to Big Bend. Day visual meteorological conditions prevailed, and no flight plan had been filed. In a written statement, the pilot reported that he had been using this private strip on the shore of the Iron Canyon Reservoir since 1965. He made several passes to check the condition of the area and noted that the lake level was higher than normal, which reduced the length of the unimproved landing area to about 600 feet. The pilot stated that on his left turn to final, the left gear contacted the surface of the water. This resulted in the airplane submerging and eventually flipping over about 100 feet short of the landing area. The pilot stated that the accident was caused by his failure to determine the proximity of the water surface. The pilot reported no preimpact mechanical malfunctions or failures with the airplane.