On February 2, 2016, at 1134 eastern standard time, a Piper PA-28-161, N8466G, ditched in the Atlantic Ocean off the coast of Miami, Florida, after a partial loss of engine power. The private pilot and the pilot-rated passenger were not injured. The airplane sustained substantial damage to the wings and the fuselage. The airplane was registered to a private company and operated by Airborne Career Academy, Fort Lauderdale, Florida, as a Title 14 Code of Federal Regulations Part 91 personal flight. Visual meteorological conditions were reported at the time of the accident, and no flight plan was filed for the flight that departed the Florida Keys Marathon Airport (MTH), Marathon, Florida, about 1100, and was destined for the Fort Lauderdale Executive Airport (FXE), Fort Lauderdale, Florida.The flight originated at FXE earlier that day. The pilot stated that when he performed the engine run-up before departure, he noted that the right magneto had a higher drop in rpm than normal. He leaned the mixture and let the engine run for about a minute before he tested the magneto again. This time the magneto had the normal drop and the pilot subsequently departed for MTH. The flight was uneventful. The pilot said that on the flight back to FXE, air traffic control instructed him to descend 500 ft, so he reduced power and turned the carburetor heat on. When he reached 500 ft, the pilot tried to increase engine RPM, but there was no response even when full throttle was applied. He switched fuel tanks and "jockeyed" the throttle a few times, but to no avail. The pilot was unable to maintain altitude and made a forced landing in the ocean about 100 ft offshore in about 15 ft of saltwater. The airplane was towed to a boat ramp and recovered. Examination of the airplane revealed it had sustained substantial damage to the fuselage and both wings. The ignition key was found in the "both" position, the fuel selector was set to the "right" tank, the throttle and mixture were full forward, and the carburetor-heat control was in the full "on" position. The left and right wing fuel tanks were contaminated with salt water and a fuel total for each tank could not be determined. The pilot reported there was about 17 gallons of fuel in each tank when they departed MTH. The engine remained attached to the airframe. The two-bladed propeller appeared undamaged and the engine was free to rotate. When the propeller was rotated, compression and valve train continuity were established to each cylinder. Engine timing was established on the left magneto, but not on the right magneto due to damage. Both magnetos were removed and disassembled. Each was filled with sand and had some salt water corrosion. Once the corrosion was removed from the right magneto's points, they opened and closed normally. No pre-accident mechanical anomalies were noted that would have precluded normal operation of the engine. Weather at Miami-Opa Locka Executive Airport (OPF), Opa Locka, Florida, about 20 miles west of the accident site, at 1125, was reported as wind from 120 degrees at 15 knots, visibility 10 miles, few clouds at 2,100 ft, overcast 3,100 ft, temperature 81 degrees F, dewpoint 66 degrees F, and a barometric pressure setting of 30.11 inches Hg. A Federal Aviation Administration-published Carburetor Icing Chart revealed a potential for serious icing at glide engine power settings, given the reported temperature and dew point conditions. The pilot held a private pilot certificate with a rating for airplane single-engine land. His last FAA second-class medical certificate was issued on July 31, 2015, with no limitations. The pilot reported a total of 86 flight hours, of which all 86 hours were in the same make/model as the accident airplane.