On September 1, 1997, about 1710, a float equipped Cessna U206F airplane, N7032Q, sustained substantial damage when it nosed over in water on the Alagnak River, 38 miles northeast of King Salmon, Alaska. The airline transport certificated pilot and two passengers were uninjured. The airplane was operated by Hartley, Inc., doing business as Branch River Air Service, of Anchorage, Alaska. The flight was conducted under 14 CFR Part 135 as an on demand air taxi. Visual meteorological conditions prevailed at the time of the accident, and a company flight plan was filed. Statements and a videotape taken by the passengers revealed that during the initial takeoff run, while on step, the pilot's seat slipped aft and he aborted the takeoff. He reset his seat, and did not water taxi the seaplane back to the original takeoff spot. The video depicts the seaplane beginning a second takeoff run, and the passengers can be heard commenting on the shallowness of the water. The seaplane then strikes a sandbar and noses over. This tape and overhead photographs show the seaplane inverted on a sandbar in shallow water.