The pilot of an amphibious airplane reported that he departed a hard surfaced runway and flew to a lake about 3 nautical miles away. He further reported that after takeoff he failed to retract the landing gear and during the touchdown on the lake, the airplane nosed over. The pilot reported that he did not use a checklist during the flight.

The fuselage and vertical stabilizer sustained substantial damage.

The pilot reported no preaccident mechanical malfunctions or failures with the airplane that would have precluded normal operation.