On July 26, 1993, at approximately 0630 Pacific daylight time (PDT), a Bell 206B helicopter, N502AH, ditched in Lake Powell after experiencing a power loss while maneuvering at low level over the water. The FAA certificated airline transport pilot and his two passengers were not injured, but the aircraft sustained substantial damage. The professional photographic flight, which departed Page Municipal Airport about 30 minutes earlier, was operating in visual meteorological conditions at the time of the accident. The aircraft was not on a filed flight plan, and there was no report of an ELT activation. The pilot, who was participating in the filming of a jet ski commercial, was maneuvering at low level in order to position the aircraft for proper filming. He passed by the left side of the jet ski at about 100 feet above the water, and then initiated a right hand climbing turn while at about 45 to 50 mph. The pilot said that as he started the turn, he checked his instruments, and everything was operating in the green with no warning lights illuminated. About three-quarters of the way around the turn, the pilot noticed that he did not feel any "power response" from the collective as he increased pitch in order to maintain his altitude. As the aircraft completed its 360 degree turn, it began descending toward the water, and the pilot realized that he had experienced a complete loss of power. He then maneuvered the aircraft into the wind, initiated an autorotation, and landed in the water in a level attitude. As the aircraft settled, the main rotor blades impacted the water, the nose pitched forward, and the aircraft sank in about 75 feet of water. A post-accident examination of the aircraft's engine and fuel control systems did not disclose any pre-impact malfunctions or anomalies that would have contributed to a power failure.