Flight Crew Air Transport Pilot (ATP); Flight Crew Flight Engineer; Flight Crew Multiengine
Flight Crew Last 90 Days 155; Flight Crew Total 30000; Flight Crew Type 32
Deviation / Discrepancy - Procedural Published Material / Policy; Ground Event / Encounter Ground Strike - Aircraft; Ground Event / Encounter Loss Of Aircraft Control
Aircraft Aircraft Damaged
Human Factors
Departed on runway 36; and retracted the landing gear.  Had previously advised the tower I intended water operations on [nearby] lake (approx 6 nm NW of ZZZ).  Flew directly to the South end of the lake to inspect landing area; and made a LH traffic pattern over the intended landing site.  While on downwind I (inappropriately) extended the gear as I would have for a land landing; and confirmed gear position via mechanical indicators and electric gear position indicators.  Normal approach and at touch down an immediate pitch forward due to extended landing gear.  Aircraft came to rest slightly past vertical in the water.  I exited the aircraft without difficulty; and as it continued to rotate to inverted; climbed aboard a float and waited for assistance.
The pilot of an amphibious aircraft reported landing on water with the landing gear extended; resulting in damage to the aircraft.