The pilot reported that the takeoff, climb, and en route portions of the cross-country flight were uneventful. He checked the wind sock prior to landing and it was "flaccid," indicating calm wind. He slowed the airplane to 80 mph on final approach and landed near the approach end of runway 5, which was 2,355 feet-long. He estimated that the airplane should have rolled to a stop; however, it continued down the runway despite heavy braking. The airplane departed the end of the runway, traveled across a small road, and down an embankment, coming to rest in the water at the edge of the airport boundary.A Federal Aviation Administration inspector examined the wreckage and reported that the airplane sustained substantial damage to the forward fuselage and submersion in salt water. There were tire skid marks on the runway leading to the wreckage. A weather buoy, located about 1 mile east of the airport, recorded wind out of the west about the time of the accident, which would have resulted in a tail wind of up to 8 knots. The pilot reported there were no preimpact mechanical malfunctions or anomalies that would have precluded normal operation of the airplane.