At about 1130 Eastern time, the airplane experienced total loss of engine power and was ditched in a marsh. Visual conditions prevailed. The airplane was substantially damaged; the private pilot was not injured. The pilot stated that she filled the airplanes fuel tanks several days before the accident flight, and even asked her flight instructor to check the tanks to make sure they were full. The flight originated about 0725. At about 1100, after an eventful flight, the engine surged. The pilot corrected by reducing power. She positioned the fuel selector to the right tank and flew for a few minutes, then repositioned the fuel selector to the left tank. She noted the left fuel quantity gauge indicated zero, though she continued flying for several minutes. The engine then began to lose power. The pilot notified ATC and requested a vector to the nearest airport. She realized that the flight was unable to land there and ditched the airplane in a marsh. Recovery personnel reported the airplane was resting in a left-wing-high attitude. No fuel or water was found in the left fuel tank. Eight gallons of salt water were drained from the right fuel tank. No fuel was noted in the water from the right fuel tank.