On August 12, 1995, at 1445 central daylight time, a Piper J3C-65 on floats, N70369, was destroyed when the private pilot lost control of the aircraft while maneuvering for landing and impacted terrain at Cedar Lake approximately 4 miles northeast of New Prague, Minnesota. The aircraft departed from Lake Francis near Elysian, Minnesota for the 14 CFR Part 91 personal flight. Visual meteorological conditions prevailed and no flight plan was filed. The pilot and his sole passenger received serious injuries. The pilot told investigators that there was light to moderate turbulence as he approached Cedar Lake for landing. He circled the landing area twice to check for debris on the water and estimated that the surface wind was southerly at 20 - 25 knots. The pilot stated that he had landed this (J3C) aircraft on this lake on previous occasions in comparable wind conditions and that it was within his capabilities. He then flew northbound from the lake on downwind leg and turned base leg in left-hand traffic over an area of tall trees north of the lake. On final approach at an airspeed "adequate" for a floatplane landing the pilot said that the right wing dropped abruptly to nearly a 90 degree angle. He applied left aileron control and full throttle and was able to level the wings however he reported that the aircraft continued to roll abruptly into a left bank to inverted flight. The nose of the aircraft dropped and the pilot, sensing that the impact was eminent, retarded the engine throttle to idle. He was again able to level the wings however the aircraft flew through an area of trees and then impacted the ground, on shore, in a wings level, nose low attitude.