On December 22, 1994, at 1630 eastern standard time, a Cessna 172C, N1620Y, lost engine power while in cruise flight near Laurel, Maryland. The airplane collided with trees during the emergency descent and was destroyed. The pilot, the sole occupant, was seriously injured. Visual meteorological conditions prevailed. The local flight departed the Suburban Airport located in Laurel at 1615 and was conducted under 14 CFR Part 91. The pilot stated that during the preflight, he found the left fuel cap off. He stated he assumed someone tried to steal some fuel. He said he continued the preflight and visually verified the fuel levels in the fuel tanks. He stated he drained all the fuel sumps, rocked the wings and again drained all the fuel sumps. He stated, "...everything looked normal." The pilot reported he started the engine and taxied the airplane to the fuel pumps, refueled the airplane, and drained the fuel sumps again. The pilot reported that he noticed no airplane anomalies up to the point when the engine started to lose power. He stated while in cruise flight at 1,200 feet mean sea level, the airplane's "...engine lost some RPM and started running rough." He stated he applied heat to the carburetor and the "...engine smoothed out immediately almost too quickly...I decided to head back to Suburban." He said that while en route back to the airport he accomplished emergency procedures to ensure all controls were positioned correctly. The pilot reported that en route to the airport the engine began to "...surge...and then go to idle." He reported, "I trimmed the airplane for best glide, rechecked the fuel selector, magnetos [and] instruments, everything was normal." He stated the engine continued to regain and lose power and the airplane could not sustain flight. The pilot stated, "I knew I wasn't going to make the runway and the woods were the only thing left. I slowed the airplane down as much as possible and aimed for a spot where I wouldn't hit a tree head on." He stated the airplane descended through trees and the fuselage came to rest on the ground. Postaccident investigation of the fuel system revealed water in the fuel. The engine was started and quit numerous times. After each engine run and failure, water was found in the carburetor fuel bowl. After the water was depleted, the engine ran without any anomalies noted. According to the pilot, the airplane was last flown about seven days prior to the accident. He stated that during those seven days there was precipitation in the area. According to the Baltimore-Washington National Weather Service Records, during the night prior to the accident the temperature was below freezing.