On May 5, 2003, approximately 1700 central daylight time, a Beech 95-C55, N541U, piloted by a commercial pilot, was substantially damaged when it overran runway 29 (3,739 feet x 100 feet, asphalt) after landing and slid down an embankment at the M. Graham Clark Airport (PLK), Point Lookout, Missouri. The runway surface was wet due to a recent rain shower, according to the pilot. The 14 CFR Part 91 personal flight had been operating on an instrument flight rules (IFR) flight plan prior to the accident. Visual meteorological conditions prevailed in the area at the time. The pilot and passenger reported no injuries. The flight departed the Memorial Field Airport (HOT), Hot Springs, Arkansas, at 1600. PLK was the intended destination. In his written statement, the pilot reported he executed an approach to runway 29 at PLK. Upon arrival he noted that it had been raining and the runway was wet. He stated that the wind conditions were gusty and the prevailing wind direction reversed to a tailwind as the aircraft touched down. He applied maximum braking, however, "the plane began to hydroplane," according to the pilot. He noted that "had it not been for the rocks on the down slope off the end of [runway] 29, the airplane would have only minor damage." The Federal Aviation Administration inspector on-scene reported that the aircraft came to rest off the end of runway 29. He noted that approximately 15 feet from the end of the pavement was an embankment. This was a drop-off, relative to the runway, of approximately 75 feet, according to the inspector. He estimated the slope as 45 degrees (downward). The terrain consisted of rocks and stones. In addition, he observed no skid marks in the area of the departure end of the runway. The pilot reported weather conditions at PLK at the time of the accident as: broken clouds at 2,000 feet above ground level (agl), overcast clouds at 4,000 feet agl, visibility 7 statute miles (sm) and wind from 180 degrees magnetic at 20 knots, gusting to 25 knots. He noted moderate turbulence and no precipitation at the time. The destination airport did not have automated weather reporting. Conditions at the Boone County Airport (HRO), located 22 nautical miles to the south-southeast, at the 1653 cdt routine observation, reported winds from 200 degrees at 6 knots and 1-3/4 sm visibility in heavy rain and thunderstorms. A special observation was recorded at 1708 cdt and reported winds from 160 degrees at 14 knots, gusting to 20 knots, and 1-3/4 sm visibility in light rain and thunderstorms. This report noted distant lightning in all quadrants. Performance data provided by the aircraft manufacturer specified a required landing distance of approximately 1,750 feet at a landing weight of 5,000 lbs. and a 10 knot tailwind. This data is applicable to a dry, paved, level surface, according to the chart. The pilot reported no malfunctions of the aircraft or engines prior to the accident.