On July 18, 1998, at 0958 central daylight time, an Anderson T Craft Special, N91XX, owned and piloted by a private pilot, was destroyed during an in-flight collision with water while in an aerobatic maneuver over Lake Sakakawea, near Pick City, North Dakota. Visual meteorological conditions prevailed at the time of the accident. The personal flight was operating under the provisions of 14 CFR Part 91 and was not operating on a flight plan. The pilot suffered fatal injuries. Time of departure is unknown. A witness stated that while he was fishing from a pontoon, an airplane flew over at an altitude of approximately 70 feet above the water. The witness reported that as the airplane passed over him, the engine rpm increased as the pitch of the aircraft increased quickly. The witness stated that while in a climb attitude the airplane rolled to the left and executed a barrel roll maneuver. The witness reported that the aircraft lost altitude during the barrel roll and impacted the water in an upright attitude, skidded on top of the water, slid onto the shore line, and impacted a tree. An autopsy was performed on the pilot in command by the North Dakota State Forensic Medical Examiner, North Dakota Department of Health, Bismarck, ND, on July 19, 1998. Toxicological testing was performed by the FAA Civil Aviation Medical Institute, Oklahoma City, Oklahoma, and quinine was detected in the urine. Negative results were obtained for all additional tests conducted.