On August 22, 2012, about 1140 eastern daylight time, a Piper PA-28RT-201T, N2970G, was substantially damaged following a ditching into the Gulf of Mexico, near Hernando Beach, Florida. The private pilot was not injured. Visual meteorological conditions prevailed, and no flight plan was filed for the personal flight, which was conducted under the provisions of Title 14 Code of Federal Regulations Part 91. The flight departed Knoxville Downtown Island Airport (DKX), Knoxville, Tennessee, about 0800 with the intended destination of St. Petersburg-Clearwater International Airport (PIE), St. Petersburg-Clearwater, Florida. According to the pilot, he fueled the airplane prior to the accident flight. While en route, the pilot maneuvered the airplane around several thunderstorms before the engine began to run rough and experienced a partial loss of power over the Gulf of Mexico. The pilot declared an emergency, searched for a place to land, and located a few islands nearby. Unable to maintain altitude, the pilot performed a gear-up landing in the water, and the airplane came to rest in approximately 3 to 4 feet of water. The pilot egressed and was rescued by the U.S. Coast Guard around 1215. The pilot held a private pilot certificate with ratings for airplane single-engine land and instrument airplane. His most recent Federal Aviation Administration (FAA) third-class medical certificate was issued June 28, 2011. He reported 4,660 total hours of flight time, of which 3,085 were in the accident airplane make and model. According to FAA records, the airplane was manufactured in 1979 and registered to the owner in 2006. It was equipped with a Continental Motors TSIO-360-FB1B, 200-horsepower engine. The airplane's most recent annual inspection was completed on September 16, 2011. At the time of the accident, the airplane had accumulated 10,507 total hours of flight time. The 1053 recorded weather observation at Hernando County Airport (BKV), Brooksville, Florida, located approximately 15 miles to the east of the accident location, included wind from 180 degrees at 7 knots, visibility 10 miles, clear skies, temperature 28 degrees C, dew point 24 degrees C; barometric altimeter 30.09 inches of mercury, and a remark of distant lightning to the north and northwest of the airport. The airplane was recovered from the water two days after the accident and moved to a salvage facility, where an engine examination was conducted on September 7, 2012. The engine remained intact and exhibited signs of salt water immersion. The variable pitch propeller was still attached, and all three blades displayed minor bending. The spark plugs were removed prior to inspection of the engine. The spark plugs showed signs of salt water immersion and of normal wear. The internal magneto timing could not be verified due to salt water damage. A visual inspection of the fuel supply line fittings revealed significant amounts of rust. The first attempt to start the engine resulted in intermittent firing. The spark plugs were removed and cleaned of salt water contamination. The engine was started a second time, which resulted in rough-running operation at a maximum power of 2,000 rpm with the fuel mixture set to full rich. A third engine run was performed, and the engine continued to run rough. Further examination revealed that the No.6 cylinder was cold. The No.6 cylinder spark plugs were removed, cleaned, and reinstalled. The No.6 fuel injection nozzle was removed and found to be clogged with debris. The nozzle was cleaned and reinstalled into the cylinder. The fourth and fifth engine runs resulted in smooth operation, and the engine reached a maximum of 2,600 rpm. The aircraft was equipped with a JBI Engine Analyzer unit. Readout of the unit at the NTSB Recorders Laboratory showed that for undetermined reasons the unit did not record the final stages of the accident flight.