On December 1, 1995, about 1700 eastern standard time, a Cessna 150M, N8779U, collided with a tree stump during a forced landing near Beaufort, South Carolina. The aircraft was operated by Master Aviation under the provisions of 14 CFR Part 91, and visual flight rules. A flight plan was not filed for the instructional flight. There were no injuries to the commercial flight instructor, nor the student, and the aircraft was substantially damaged. The flight departed Hilton Head, South Carolina, at 1600 on the same day. The pilot reported that he fueled the airplane at Hilton Head, prior to takeoff, with six gallons of aviation gasoline. All six gallons were added to the right tank. About ten minutes after refueling, the student pilot performed a pre-flight inspection, that included sampling the fuel from the tank drains. Shortly after take off, while the aircraft was in cruise flight, the engine quit. The instructor executed a forced landing. On landing roll, the aircraft struck a tree stump, twisting the fuselage, and buckling the tail cone. The pilot stated that after the forced landing, he drained fuel from the right wing and the sump. According to him, both samples contained water. Upon further examination of the engine, no other engine problems were found.