On May 17, 2020, at 1145 Pacific daylight time, a Beechcraft BE-35 airplane, N8359D, was substantially damaged when it was involved in an accident near Cascade Locks, Oregon. The pilot received minor injuries, and the passenger was not injured. The airplane was operated as a Title 14 Code of Federal Regulations (CFR) Part 91 personal flight. According to the pilot, after performing a thorough preflight and run up inspection, he and his passenger departed on a personal flight. The takeoff was normal, and the fuel selector valve was set to the LEFT MAIN position. About 20 minutes into the flight, the pilot switched the fuel selector valve to the AUX TANK position and shortly after initiated a return to the departure airport. During the return flight, he decided to familiarize himself with a local airport. The pilot announced his position on the common traffic advisory frequency (CTAF) and his intention to conduct a low approach to the runway. While on final approach, the pilot observed a person standing on the north side of the runway more than half-way down the runway. After overflying the person, the pilot advanced the throttle to full power and retracted the flaps. About 1-2 seconds after initiating a climb, the pilot noted a lack of acceleration and the engine volume decreased. He returned the airplane to level flight and switched the fuel selector from the AUX TANK position to the RIGHT TANK position. The pilot looked for a suitable landing area and made sure that his throttle, mixture, and propeller levers were full forward. The pilot reported a rocky shoreline and with no other options, set up for a forced landing to the water. The airplane landed in the water near the shoreline, and the pilot and passenger were able to exit the airplane without assistance and swam to shore. The airplane was recovered from 20 ft of water less than a mile from the airport, and after recovery from the water, a postaccident examination was conducted. The spark plugs were removed from the engine; their electrodes were intact, and no indication of mechanical damage was observed. The engine was rotated at the propeller and valve train continuity and thumb compression was obtained on all cylinders. Both magnetos were removed; they were rotated, and spark was produced at all terminal leads. Examination of the fuel selector revealed it was selected to the RIGHT TANK position. Additionally, printed on the fuel selector plate were the words “AUX TANK, LEVEL FLIGHT ONLY.”