On September 12, 1999, at 1327 eastern daylight time, a Lake LA-4, N1137L, sustained substantial damage during a landing on Bruin Lake, about 18 miles northwest of Ann Arbor, Michigan. The airline transport rated pilot received serious injuries. The personal 14 CFR Part 91 flight was operating in visual meteorological conditions. No flight plan was on file. The local flight departed Pontiac, Michigan, about 1300. The pilot told police authorities that he was going to practice a touch and go landing on the lake. He said that on touchdown the airplane decelerated as if "the brakes were locked." The pilot said he did not know what caused the accident. The pilot did not indicate any mechanical problem with the airplane. Subsequent to the accident an examination of the wreckage was conducted. The Federal Aviation Administration inspector said the airplane was broken into three major pieces and was recovered from the lake the day following the accident. He said his examination of the wreckage failed to reveal any pre-impact anomalies. He said landing gear was in the retracted position. He said that when he talked to police authorities they told him, "According to witnesses [the pilot] was attempting a landing on Bruin Lake when he lost control of the aircraft. One of the sponsons hit the water causing the aircraft to flip."