The amphibian pilot departed from a paved runway, and planned a water landing on a lake near a small island. At touchdown, the airplane nearly nosed over, came to rest upright, but ultimately sank. The forward section of the hull, wing struts, wing structure, and landing gear all sustained damage during the accident sequence. The pilot later stated that he failed to raise the landing gear after his initial departure from the runway, and he never used the checklist onboard the airplane during the flight.