On July 11, 2012, about 1830 central daylight time, a Piper PA-28-140, N6258J, operated by a private individual, was substantially damaged during a forced landing to a swamp, following a partial loss of engine power during initial climb from Ferguson Airport (82J), Pensacola, Florida. The private pilot incurred minor injuries and the flight instructor was seriously injured. The instructional flight was conducted under the provisions of 14 Code of Federal Regulations Part 91. Visual meteorological conditions prevailed and no flight plan was filed for the planned local flight review. The private pilot stated that the taxi and takeoff roll were normal. As the airplane crossed over a treeline on the south side of the airport, both pilots noticed that the airplane was not climbing well. They then noticed that the rpm gauge indicated 2,100. With partial power remaining, the pilots flew a left-hand traffic pattern to return to the departure runway. The airplane was able to climb at 200 feet-per-minute to 400 feet above ground level. While on the downwind leg, the engine began to sputter and lost more power. They then turned toward the runway about midfield; however, the airplane impacted a swamp prior to the runway. Examination of the wreckage at the accident site by a Federal Aviation Administration (FAA) inspector revealed that the airplane came to rest upright, oriented on a heading of 260 degrees, in about 2 to 3 feet of swamp water. The left wing separated during the impact and the right wing remained attached. The inspector drained approximately 12 gallons of fuel from the right wing fuel tank and 10 gallons from the left wing fuel tank. The fuel did not exhibit any visible contamination. The top spark plugs were removed and their electrodes were unremarkable. The propeller was rotated by hand and crankshaft, camshaft, and valve train continuity were confirmed to the rear accessory section. Additionally, thumb compression was attained on all cylinders. An NTSB investigator and representative from the engine manufacturer further examined the wreckage following its recovery from the swamp. The examination revealed that the propeller assembly remained attached to the propeller crankshaft flange. The propeller spinner was crushed and did not exhibit rotational damage. One propeller blade was not damaged and the remaining propeller blade had a gouge on the trailing edge. The oil suction screen was removed and no contaminants were noted. An unmeasured amount of oil was present in the engine. The oil filter was removed and opened. The filter media was free of contaminants. The fuel lines from the airframe to the engine driven fuel pump remained attached. The fuel lines were disconnected for examination and no fuel was present. The engine driven fuel pump was actuated by hand and pumped water when an inlet line was submerged in a bucket of water. The airframe gascolator was damaged and open to the elements. The induction air filter and air box, along with the associated scat tubing was impact damaged and found in the cabin with part of the cowling. The carburetor had fractured and the bowl section separated. The carburetor fuel inlet screen was examined and was free of contaminants. The throttle and mixture controls were damaged. They remained attached to the carburetor, but their positions were unreliable. The left and right magnetos were rotated by handed and produced spark at all ignition towers. The top and bottom ignition harnesses were not damaged. All spark plugs were removed. Their electrodes were intact and they varied in color from dark brown to light brown, except for the No. 1 bottom spark plug, which was oil soaked. The vacuum pump remained attached and was not damaged. The drive gear was rotated freely by hand. The vacuum pump was disassembled and the carbon rotor vanes were intact. The NTSB investigator also rotated the propeller by hand and confirmed crankshaft, camshaft, and valve train continuity to the rear accessory section of the engine. Review of maintenance records revealed that the airplane's most recent annual inspection was completed on November 1, 2011. At that time, the airplane had accumulated 3,406 total hours of operation. The airplane had flown 22 hours from the time of the annual inspection, until the time of the accident. Comparison of the recorded temperature and dew point to an FAA Carburetor Icing Chart revealed no susceptibility to carburetor ice at the time of the accident.