On October 5, 2003 at 1630 eastern daylight time, a Stinson 108-3, N831C, registered to and operated by a private pilot, collided trees and sank in water near Lake Placid Florida. The personal flight was operated under the provisions of Title 14 CFR Part 91 and visual flight rules. Visual meteorological conditions prevailed at the time of the accident and no flight plan was filed. The private pilot and two passengers were not injured and the airplane was substantially damaged. The flight departed Lake Wales Municipal Airport, Lake Wales, Florida, on October 5, 2003, at 1520. The pilot reported that he completed a preflight inspection of the airplane and found no problems with the airplane. After take off, the pilot, reported that he was flying over Lake June at 400 feet when he entered a 180-degree steep turn. When the pilot rolled out of the turn, the airplane descended, collided with a tree adjacent to the lake, and subsequently sank into the water. Examination of the airframe revealed that the airframe was twisted and the floats were damaged. The pilot did not report a mechanical problem with the airplane during the flight.