THE PRIVATE PILOT WAS TO FERRY THE AIRCRAFT FROM A PRIVATE, GRASS FIELD TO A LOCAL AIRPORT SO THAT AN ANNUAL INSPECTION COULD BE PERFORMED. AFTER ABOUT 30 MINUTES OF GROUND OPERATION TO FAMILIARIZE HIMSELF WITH THE HANDLING CHARACTERISTICS OF THE AIRCRAFT, HE ADDED FUEL AND PREPARED FOR TAKEOFF. DURING THE TAKEOFF ROLL, HE NOTICED THAT ACCELERATION WAS NOT VERY GOOD; HOWEVER, THE ENGINE WAS RUNNING SMOOTHLY. AFTER ROTATION, HE REALIZED THAT THE AIRCRAFT WOULD NOT CLEAR PERIMETER TREES, SO HE CLOSED THE THROTTLE AND ATTEMPTED TO FLY BETWEEN THEM. THE AIRCRAFT COLLIDED WITH TREES, THEN FELL INTO AN ADJACENT WATERWAY. THE PILOT LATER REPORTED THAT THE 1,100 FOOT LONG RUNWAY CONSISTED OF WET GRASS, WITH AREAS OF SOFT SAND. ON THE TAKEOFF ROLL, HE PULLED BACK ON THE STICK TO AVOID ROUGH AREAS. HE ALSO REPORTED THAT THE PREVAILING HEAD WIND HAD SHIFTED TO A TAIL WIND.