THE PILOT HAD COMPLETED A VOR/DME APPROACH AND HAD SIGHTED THE AIRPORT AT CIRCLING MINIMUMS (620 FEET). HE CONTINUED THE DESCENT AND TOUCHED HALFWAY DOWN THE 2494 FEET RUNWAY. THE RUNWAY WAS WET, THE PILOT COULD NOT STOP THE AIRPLANE ON THE RUNWAY PAVEMENT, AND OVERRAN THE RUNWAY INTO HIGH VEGETATION AND WOODS.