On June 4, 1997, about 1300 Alaska daylight time, a float equipped Piper PA-18, N91855, crashed during landing on a lake, about 7 miles west of Anchorage, Alaska. The airplane was being operated as a visual flight rules (VFR) local area instructional flight when the accident occurred. The airplane, operated by Alaska Air Academy, Anchorage, sustained substantial damage. The certificated commercial pilot/flight instructor (first pilot), and the certificated commercial pilot/dual student (second pilot), were not injured. Visual meteorological conditions prevailed. The flight originated at the Lake Hood Seaplane Base, Anchorage, about 1200. On June 5, 1997, at 0800, the first pilot reported in a telephone conversation with the National Transportation Safety Board (NTSB) investigator-in-charge (IIC), that he was providing seaplane instruction to the second pilot. The second pilot was seated in the front seat of the airplane and was performing a simulated forced landing on Twin Island Lake. During the landing approach, about 20 feet above the water, the rate of descent increased to about 300 feet per minute. Both pilots added throttle but the airplane touched down hard on the water. The airplane received damage to a fuselage longeron at the forward float attach point.