On May 5, 1996, about 1654 eastern daylight time, a Cessna P206D, N8744Z, was substantially damaged when the airplane was ditched in a reservoir during a visual approach to Westchester County Airport, Harrison, New York. The private pilot and pilot rated passenger were not injured. Visual meteorological conditions prevailed for the local flight that departed about 1630. The personal flight was conducted under 14 CFR Part 91. In the NTSB form 6120.1/2, the pilot reported that he and a passenger departed Westchester County Airport on a local flight with the intent to demonstrate the airplane to the passenger, a prospective partnership buyer. During the return flight, while in cruise, the pilot stated that "the engine suddenly started shaking violently. . . .Then smoke started coming out of the front of the engine compartment. Suddenly the engine and [propeller] stopped cold. I realized that we could not make it to the runway and we then quickly decided to head for the water." The passenger reported that during the visual approach to runway 34 at 1400' MSL the engine lost power and blue smoke entered the cabin. He observed the tachometer at 2000 RPM and then about 1000' MSL, the engine lost total power, and the propeller stopped. Postaccident examination by a Federal Aviation Administration Inspector revealed a 1" square hole in the crankcase in the vicinity of the number two cylinder. The engine was examined by Alphin Aircraft Inc., Hagerstown, Maryland. The examination revealed that the number one connecting rod bolt had separated; however, the bolt was not located for further examination.