On September 5, 1993, at approximately 1600 Alaska daylight time, a float-equipped Cessna 180 airplane, N180TM, dragged a wing and overturned while taxiing on Sweet Lucy Lake, 35 miles north of Port Alsworth, Alaska. The airplane sank, and the private pilot and three passengers escaped without injury. No flight plan wa on file for the flight to be conducted under 14 CFR Part 91 for personal reasons. Visual meterorological conditions existed at the time. The airplane remained submerged on September 8, 1993, and had incurred substantial damage. The pilot told investigators that he had attempted to sail backwards in the strong southeast wind, but when he added power to taxi, the left wing picked up, the right wing dragged and the airpalne flipped over and sank. He said all of the occupants swam out and there were no reported injuries. No NTSB Form 6120.1/2 has been received on this accident and therefore some data is estimated or left blank by the investigator.