Date: 201910
Local time of day: 0001-0600
Location: ZZZ.Airport, US
Flight conditions: VMC
Weather elements / visibility: Clear; 10
Light: Daylight
Aircraft: LA-4-200 Buccaneer
Operator: Personal
Operating under: Part 91
Flight plan: None
Mission: Training
Flight phase: Takeoff / Launch
Reporter organization: Personal
Reporter function: Instructor
Reporter qualification: Flight Crew Air Transport Pilot (ATP); Flight Crew Flight Instructor; Flight Crew Multiengine; Flight Crew Instrument
Human factors: Confusion; Distraction; Time Pressure
Anomaly: Aircraft Equipment Problem Less Severe; Ground Event / Encounter Loss Of Aircraft Control; Ground Event / Encounter Object; Ground Event / Encounter Ground Strike - Aircraft
Detector: Person Flight Crew
When detected: In-flight
Result: Aircraft Aircraft Damaged
Contributing factors: Environment - Non Weather Related
Primary problem: Environment - Non Weather Related

Narrative: The area we were training in was ZZZ. We initially approached ZZZ from the south end; with aircraft configured for a water landing; and proceeded to survey ZZZ for a suitable water landing area. The main part of ZZZ was unsuitable; but the water surface in the lake's arm seemed alright for a water landing and to conduct water work. After having surveyed the area for a suitable area to land; we landed east of the big island and settled into a displaced taxi. We landed into the wind; with wind speed about 10 kts. out of the southeast (direction). I took the moment while in the water in displaced taxi to demonstrate both idle and plow taxis to my student. I reversed course and went downwind at idle taxi speed to allow for more distance for a water takeoff. Once oriented into the wind; which was from the southeast; I held full-aft elevator and applied full power. Once the bow wave was sufficiently back; I applied full forward elevator. Aircraft achieved a step taxi condition and was accelerating. My last recollection of the airspeed indicator was 30 mph indicated. Water surface conditions at the time of this water takeoff were a little rough; but nothing I hadn't experienced before. It was my intent to take off and survey the water and make a decision about whether to continue or conclude the lesson for the day. The problem started when I felt a thump and the nose of the airplane pitched upward and then back down. I estimate that the aircraft flew to the height of about 5 ft. before going back down to the water. As I descended; the aircrafts nose struck the water and then began to pitch up again. I arrested the oscillations by idling the airplane and applying full aft elevator in order to stall it into the water and stop any further porpoising. Back on the water in full displacement and under control; I realized we had sustained some damage because the airplane was listing to my left. I glanced to the left and determined there was wing tip damage and noticed that the left sponson was gone. Knowing that there was a potential for sinking; I headed to the nearest beach in order to prevent any further damage. Once safely on the beach; I checked on the student and found no injuries had occurred. I contacted [FBO] to inform him of the situation.




Synopsis: A Lake Buccaneer Instructor pilot reported striking a foreign object while demonstrating a water takeoff; causing damage to the aircraft.