On December 2, 2002, about 1430 eastern standard time, a Consolidated Aeronautics, Inc., LA-4-200, N6193V, registered to a private individual, collided with a buoy located on the Apalachicola River, near Blountstown, Florida. Visual meteorological conditions prevailed at the time and no flight plan was filed for the 14 CFR Part 91 instructional flight. The airplane was substantially damaged and the certified flight instructor (CFI) and pilot-rated student were not injured. The flight originated about 1300, from the Apalachicola Municipal Airport, Apalachicola, Florida. The airplane owner/pilot-rated student stated that after takeoff while flying over the Apalachicola River, the CFI advised him that he wanted to demonstrate an engine-out landing on water, and took the flight controls. The CFI landed the airplane on the water then applied power to takeoff. During the takeoff run and on step taxi facing a green colored buoy ahead, the CFI asked him what side of the buoy to go on. The owner/pilot-rated student stated that he replied the left side, and the CFI maneuvered the airplane to the left, but a portion of the right wing collided with the buoy. The airplane rotated 90 degrees to the right and came to rest. The airplane was taxied on the river to a boat ramp where the airplane was secured. The CFI advised him that the occurrence was an incident and not an accident, therefore; was not reportable. The CFI stated that the training flight departed from Apalachicola Municipal Airport with the owner-operator in the left pilot seat, and himself (CFI) in the right seat. The CFI demonstrated a power-off emergency landing on the Apalachicola River and while water taxiing approaching a marine channel marker, the aircraft encountered a rogue current or submerged object. The airplane was turned to the right causing the right wing tip to impact the channel marker. The aircraft was then water taxied upstream to a boat launching ramp where the airplane was taxied onto land and secured. The occurrence was reported by the airplane owner to the NTSB on February 19, 2003. The NTSB determined the airplane was substantially damaged and was classified an accident.