On a previous flight, the pilot of the amphibious light sport airplane had pulled the landing gear circuit breakers to mitigate the risk of accidentally raising the landing gear while on the ground. Prior to the accident flight, which departed from a hard-surface runway, he serviced the airplane with fuel and performed a preflight check. He intended to perform water landings on an adjacent lake, and after takeoff he selected the gear-up switch but had forgotten to reset the circuit breakers. Shortly after takeoff he felt a light airframe vibration and decided to expedite the landing. While circling the landing spot, and slowing the airplane for the approach, the gear misconfigured warning sounded. However, the pilot silenced the warning because his attention was diverted by the landing due to the vibration, so the gear remained extended as the airplane touched the water. The airplane then nosed over and sustained substantial damage. The “before engine start” checklist in the pilot’s operating handbook states that the circuit breakers should be in. There is no reference in the handbook to pulling the circuit breakers to prevent accidental activation.