On July 5, 2003, about 1430 central daylight time, an Aviat A-1B, N700KY, operated by a commercial pilot, sustained substantial damage when the wing strut failed upon landing on Lake Oahe near Pierre, South Dakota. The 14 CFR Part 91 personal flight was operating without a flight plan. Visual meteorological conditions prevailed at the time of the accident. The pilot and passenger reported no injuries. The flight departed from the Pierre Regional Airport (PIR), Pierre, South Dakota, about 1400 and had the Bismarck Municipal Airport, near Bismarck, North Dakota, as its final destination. The flight was landing on Lake Oahe for a stop over at the time of the accident. According to the pilot, he and a passenger were about 30 miles north of PIR and were going land on the Oahe Reservoir. The pilot reported making "a high recon approximately 100 yards from east shore then low recon, set up on downwind, base, final." The pilot stated that upon landing that he "heard a crack from [the] left front. As we slowed and [the] nose began to drop the [aircraft] began [a] slow lean to [the] left." According to the pilo, the airplane continued to lean until the left wing tip touched the water. A boater assisted the pilot in bringing the aircraft to the shore. The pilot reported a failure of the landing gear strut on the left front float. At 1453, the PIR recorded weather was: Wind 140 degrees at 7 knots; visibility 10 statute miles; sky condition clear; temperature 32 degrees C; dew point 17 degrees C; altimeter 29.82 inches of mercury. PIR is located about 25 miles south-southeast of the accident site. Federal Aviation Administration inspectors examined the airplane. An inspector stated, "... No evidence of a pre-existing metal problem could be determined."