On September 7, 2002, about 1230 eastern daylight time, a Robinson R-22B, N707RG, was substantially damaged after it impacted a lake and sank while maneuvering near Jamestown, Kentucky. The certificated commercial pilot and passenger were not injured. Visual meteorological conditions prevailed and no flight plan had been filed for the aerial photography flight conducted under 14 CFR Part 91. According to a Federal Aviation Administration inspector, the helicopter was being utilized by a photographer to take pictures of boats during a race conducted on Lake Cumberland. The pilot said the helicopter was about 200 feet above the lake, and he had been flying for more than an hour, when he spotted a boat that was not previously photographed. The pilot made a left turn and began a decent to keep pace with the boat. He further stated: "...I noticed an abnormal sink rate and put in aft cyclic. The rate did not arrest, so I brought in more aft cyclic along with collective power. As I came into about 50 to 100 feet agl, I heard a low RPM warning horn. I continued to slow the [helicopter], while rolling on throttle. The descent rate brought the [helicopter] in contact with the water." The helicopter sank and came to rest at a depth of about 115 feet. It was not recovered. The pilot reported approximately 1,437 hours of total rotorcraft flight experience, which included about 650 hours in make and model. The helicopter was maintained under a manufacturer’s inspection program, and was inspected the day before the accident. It had been operated about 7 hours since the inspection. The helicopter was manufactured in 2001 and had accumulated about 505 hours since new.