On September 14, 2005, about 1845 eastern daylight time, a Grumman AA-5A, N9954U, registered to and operated by a private individual as a Title 14 CFR Part 91 personal flight, crashed into a marsh in Ponte Vedra Beach, Florida. Visual meteorological conditions prevailed, and no flight plan was filed. The airplane received substantial damage and the private pilot was uninjured. The flight originated from Ormond Beach, Florida, the same day, about 1645. The pilot/owner stated that prior to the accident, he had recently purchased the airplane and it had been given a pre-purchase inspection as a condition of purchase. He further stated that during the course of the inspection some minor discrepancies were noted, and all were corrected by an FAA licensed airframe and powerplant mechanic. On September 3, 2005, he stated that he took possession of the airplane, and as he flew the airplane and during the course of leveling off at 1,000 feet after takeoff during a practice/familiarization flight, as he configured the airplane for cruise flight, as soon as the electric fuel pump was secured the engine sputtered and ceased operating. The pilot said that the dealer through whom he had purchased the airplane then took control and landed the airplane uneventfully in an open field. After the forced landing the pilot said that an airframe and powerplant inspector then inspected the fuel system and flushed the fuel tank and fuel lines 3 or 4 times, and concluded that the engine had ceased operating due to water contamination in the fuel system. On the day of the accident, another pilot ferried the airplane to the location where he then took possession of it. The pilot who ferried it reported that he had difficulty starting the airplane, and that a mechanic was needed get it started. The pilot/owner further stated that after arriving and conducting a preflight inspection, and concluding that it was safe to fly the airplane, he took off, en route to Jacksonville, Florida, where he intended to perform pattern work and instrument training. He said that he climbed to 2,000 feet, secured the electric fuel pump, noting the pressure still in the green, established cruise flight at 2,000 feet, decreased throttle to 2500 rpm, and leaned the mixture to slightly less than peak EGT. More than 30 minutes later, at about 1720, he said the engine began to sputter and it ceased operating. He immediately switched on the electric pump, noting the pressure in the green band, and attempted to restart the engine. He said that the engine may not have ceased operating altogether, and may have been idling at approximately 1,000 rpm, because the propeller was windmilling during the forced landing. He said he conducted emergency procedures, and made a forced landing into the marsh. During the landing the airplane flipped upside down and came to rest inverted, partially submerged in the water. Postcrash examination of the accident airplane was performed by an FAA licensed airframe and powerplant mechanic, under the supervision of an FAA airworthiness inspector. According to the FAA inspector, after recovery from the water, the detailed examination included examination of the airframe, engine and flight controls, and no anomalies were noted. The inspector and mechanic both confirmed that when the engine and accessories were examined, oil and water was drained from the sump and cylinders, and the valve covers and spark plugs were removed and examined. they said that no anomalies were noted with the fuel system, and only water immersion related contamination was found in the carburetor. In addition, they said that the magnetos were removed examined, and tested with sparks being obtained on all terminals. In addition, the crankshaft was rotated and continuity of the valve system and drive train was obtained throughout the engine, with thumb compression being noted on all cylinders.