The flight instructor of the Cessna 152 stated to a Federal Aviation Administration (FAA) inspector that during the preflight inspection, he and the student pilot found water in the fuel tanks when sumped. They continued draining the fuel until no water was found in the fuel samples obtained from the wing tank and gascolator. Their 1-hour instructional flight was uneventful. They returned to the departing airport, landed and took a short break from flying. The instructor and student pilot returned to the airplane to continue training, and were going to stay in the traffic pattern of the airport. The fuel system was not sumped before the second flight. During the initial climb after the first touch-and-go, the engine lost all power about 300 feet above the ground. The flight instructor took over control of the airplane and elected to land on a golf course fairway adjacent to the airport. The airplane touched down on the fairway, striking trees before coming to a stop. During the on-scene examination of the wreckage by FAA inspectors, 6 ounces of water was removed from the gascolator. The right fuel tank cap had stains consistent with leaking and possible infiltration into the fuel tank.