On October 5, 2002, at 1430 central daylight time, a Cessna 172L, N713SX, owned and piloted by a private pilot, was substantially damaged during an approach for landing on Fish Lake approximately 6 nautical miles north of Little Falls, Minnesota. The left float contacted the water while the airplane was in a banked turn. Visual meteorological conditions prevailed at the time of the accident. The 14 CFR Part 91 personal flight was not operating on a flight plan. The pilot was uninjured. The flight originated from Lake Alexander approximately 17 nautical miles northwest of Little Falls, Minnesota, at 1400. The pilot stated that at 100 feet above ground level (AGL) he reduced speed to 65 mph. As he entered ground effect, he added power to keep the airplane flying as he was still about a mile from the south shore of the lake where his passenger was waiting. He was flying about 20 feet above the water and noticed that he was not lined up perfectly with the wind so he made a slight turn to the left as he started to raise the nose in preparation to flare. He stated that his depth perception must have been off. He then felt the left float contact the water. He tried pulling the elevator back but could not gain control. The right wing then hit the water hard as the airplane turned to the left. He described the lake conditions as being glassy at the south end of the lake with light ripples near the landing area. The pilot stated that his safety recommendation is to never make turns on short final and to execute a go-around if things are not right. He added that the turn he made was very small but it was enough to drop a wing. He also stated to treat light rippled water as glassy water.