On September 10, 2004, at 1215 central daylight time, a float equipped Williams Glastar GS-1, N501YR, collided with trees following a loss of control during takeoff on Scott Lake in Hayward, Wisconsin. The private pilot and passenger were seriously injured. The airplane was substantially damaged. The 14 CFR Part 91 personal flight was operating in visual meteorological conditions without a flight plan. The flight was originating at the time of the accident. The planned destination was Cranberry Lake, Eagle River, Wisconsin. The pilot reported that prior to takeoff he added one notch of flaps, raised the water rudders, and let the airplane weather vane into the wind. He reported that during the takeoff the airplane "... buffeted as if the wind direction was changing rapidly." The pilot reported he was over the trees at the end of the lake at an airspeed of 60 miles per hour (mph) and an altitude of 150 feet above ground level (agl), when the airspeed went to zero and the right wing dropped. He reported that he corrected by applying aileron, but the airplane rolled to the left. He reported the airplane leveled out at an altitude of about 100 feet agl prior to experiencing a "... total loss of lift... ." The pilot stated he attempted to get the airplane as close to shore as possible. The airplane came to rest on a beach with the right wing in the water. A Federal Aviation Administration Operations Inspector reported that during an interview, the pilot stated he used two notches of flaps for takeoff and he applied full flaps when he was having difficulty gaining altitude. The pilot reported , "Wind shear on takeoff, the magnitude of which I experienced that day is hard to predict... ." The wind reported at the Sawyer County Airport, Hayward, Wisconsin, at 1153, was from 170 degrees at 14 knots, gusting to 18 knots.