ATL84FA026

While en route, the acft's radio transmitter became inop; however, the plt could receive transmissions & was provided vectors toward the destination arpt. After starting a descent near the destination, the eng lost power. Subsequently, the acft was ditched in the Tennessee river. A water land eng was chosen because of the rough terrains & darkness. After the water landing, all 4 occupants exited the acft while it was still floating. According to the plt, none received injuries during the forced landing. One of the passengers could not swim. She & one other passenger were presumed to have drowned. After the acft was recovered, only river water was found in the fuel tanks. The acft had flown about 4 hrs & 6 min prior to crashing. Fuel consumption for the flt as estimated to be 60.27 gal. The fuel capacity for the acft was 60 gal. It was noted that the non-instrument rated plt was briefed to expect IMC conditions along the route of flt. During the flt, he had cruised at 8000 ft. at chattanooga, the ceiling was 3000 ft.