On March 17, 2023, at 1414 eastern daylight time, a Beech V35, N5616S, was substantially damaged when it was involved in an accident near Shoreham, New York. The pilot and pilot-rated passenger were not injured. The airplane was operated as a Title 14 Code of Federal Regulations Part 91 personal flight. According to the pilot, he had previously “topped off” the fuel tanks, and on the day of the accident he performed a preflight inspection of the airplane and noted no anomalies. Then, he departed Brookhaven Airport (HWV), Shirley, New York, for a local flight. About 20 minutes into the flight, at a cruise altitude of 3,500 ft mean sea level, he noticed that the manifold pressure went up while at the same time the rpm decreased. The pilot attempted to regain engine power by switching fuel tanks, switching magnetos, and giving the engine an alternate air source; however, the engine did not respond. He noticed that the ocean tide was low and elected to land on the beach. The airplane landed hard, the landing gear collapsed, and the left-wing spar was substantially damaged. The airplane veered left and came to rest in the water. Throughout the accident sequence, the pilot noted that the propeller was “slowly” windmilling. Examination of the engine revealed that it contained 12 quarts of oil. The top spark plugs were removed. The No.1 top plug was oil fouled. The Nos. 2, 3, and 5 were all contaminated from saltwater submersion. Fuel was observed in the fuel line to the engine-driven fuel pump and the engine fuel divider. The engine-driven fuel pump was removed and the shaft was found intact. The fuel pump was turned by hand with no anomalies noted. All cylinders were examined with a lighted borescope; however, the cylinder walls and valves were obscured by saltwater corrosion. The fuel injectors were removed and visually inspected for blockage; they were not obscured. The magnetos were examined and filled with salt water. Examination of the engine did not reveal any anomalies that would have precluded normal operation.