The pilot in the amphibious float-equipped airplane reported that he intended to perform a water landing. On the downwind leg of the approach, he performed his prelanding checks from memory, and he confirmed that the three green landing gear safe lights were illuminated. However, he added that he "should have looked for blue lights." The pilot landed on the water with the landing gear wheels extended, and the airplane pitched forward and nosed over. The airplane sustained substantial damage to the right wing, the empennage, and the windscreen. The pilot asserted that he "should have used a checklist once airborne. Both the after takeoff and before landing checks would have saved me from this event." The pilot reported that there were no preaccident mechanical malfunctions or failures with the airplane that would have precluded normal operation.