On August 4, 2001, about 1530 central daylight time, a Morton S. Dismuke Spencer Amphib 1-12E, N112MD, registered to an individual, crashed while performing high speed taxiing on Perdido Bay, near Pensacola, Florida, while on a 14 CFR Part 91 personal flight. Visual meteorological conditions prevailed at the time and no flight plan was filed. The airplane received substantial damage and the private-rated pilot and one passenger were not injured. The flight originated from Coastal Airport, Pensacola, Florida, the same day, about 1400. The pilot stated that after departing Coastal Airport, they flew to Ferguson Airport for fuel. After refueling, they departed Ferguson Airport and performed five water landings and takeoffs. They landed on Perdido and to perform water maneuvers. During the first water maneuver the airplane developed a tendency to turn to the right as it gained speed. On the second maneuver, at 20 to 25 knots, the airplane again started turning to the right. He reduced engine power to investigate what was wrong, and when he did the right wing went further into the water and the airplane turned over inverted. The left wing went into the water and contacted the bottom of the bay. Their intentions, had the accident not occurred, was to take off after high speed taxiing and return to Coastal Airport. Postcrash examination of the airplane by an FAA inspector showed the right float was damaged during the accident and it could not be determined what caused the airplane to turn right during water operations.