On August 25, 1993, at 1030 eastern daylight time, a Piper PA22, N5061Z, ditched in a river near McCaysville, Georgia. The personal flight operated under 14 CFR Part 91 with no flight plan filed. Visual weather conditions prevailed at the time of the accident. The airplane sustained substantial damage and the private pilot and passenger received minor injuries. The flight departed Copperhill, Tennessee, at 1025 hours. A layer of fog prevented an early departure as planned by the pilot. The pilot refueled with 11 gallons of aviation fuel and completed a preflight inspection. As the fog condition improved, the pilot completed an engine runup and attempted a takeoff. He aborted the takeoff and returned for another takeoff. The pilot reported that the airplane did not accelerate sufficiently for a safe takeoff, and that the engine developed a rough condition. The pilot completed another engine runup that included a check of the carburetor heat system; all systems operated normally. A second takeoff and liftoff were completed but as the airplane climbed through 250 feet the engine developed another rough condition. The pilot selected a nearby river, and established an emergency descent for a forced landing; the airplane ditched in the river. The subsequent retrieval and examination of the airplane failed to disclose a mechanical malfunction or component failure. An examination of the weather data disclosed that conditions were favorable for the formation of carburetor ice.