Following take-off from a land base, the pilot of the float-equipped Otter forgot to raise the landing gear and proceeded to McKenzie Lake where, following inspection of the landing area, he carried out his pre-landing check and prepared for a glassy water landing. Shortly after the float- equipped aircraft touched the water, it flipped over on its back. The pilot easily vacated the aircraft through the already open window of the port cockpit door and inflated his mae west. The report found that the pilot failed to complete a thorough pre-landing check. He was also criticised for failing to carry a crewman or second pilot in a float-equipped aircraft, contrary to flying orders.