On August 5, 2020, about 1333 eastern daylight time, a Piper PA-25-235, N223AB, was substantially damaged when it was involved in an accident near Miami, Florida. The pilot was not injured. The airplane was operated as a Title 14 Code of Federal Regulations Part 91 banner tow flight. The pilot picked up a banner and climbed on an easterly heading to 1,300 ft mean sea level (msl). He leaned the mixture, then at the top of the climb he checked the carburetor heat by applying it for 15 to 30 seconds and noted a 100-rpm drop. He removed carburetor heat and flew in a southeast direction, then proceeded in a southerly direction. He flew over the Port of Miami at 1,100 ft msl where he checked the carburetor heat a 2nd time, applying it and leaving on for 15 to 30 seconds, again noting a 100-rpm drop. He removed carburetor heat and continued in a southerly direction. When the flight was south of Fisher Island, he made a radio call on the Watson Island Advisory air-to-air frequency that the flight was at 1,100 ft msl, turning to the north, descending to 700 ft msl. He applied carburetor heat before beginning to descend, but before he had time to adjust the throttle control, the engine rpm dropped to between 1,000 and 1,200. The pilot maneuvered the airplane over water where he dropped the banner. With full power applied, the mixture leaned, and carburetor heat on it felt to him like the engine was not producing power. He picked out the landing site, checked the magnetos, applied full rich mixture and with carburetor heat still applied, he descended to between 50 and 100 ft. About that time the engine sputtered "like it wanted to come back," but it did not recover. Just before touchdown he pulled the throttle and mixture controls and was fast at the intended landing site. The airplane touched down and collided with a fence. He reported that the engine was stopped when he came to rest, and he then secured the airplane. According to the Federal Aviation Administration (FAA) inspector who examined the airplane at the accident site, there was no fuel contamination in the fuel tank or airframe fuel strainer, and only scratches to the propeller blades, though the propeller spinner was damaged. While he and the pilot were present, a company employee started the engine and briefly operated it to idle. Following recovery of the airplane an inspection of the carburetor heat system revealed no discrepancies. The engine was operated using the fuel that was in the fuel tank at the time of the accident. At 1353, the weather reported at Miami International Airport (MIA), about 8 miles west-northwest of the accident site, included a temperature of 28°C and a dew point 25°C. The calculated relative humidity at those conditions was about 80%. Review of the icing probability chart contained within FAA Special Airworthiness Information Bulletin CE-09-35 revealed the atmospheric conditions at the time of the accident were "conducive to icing at glide [idle] and cruise power."