On September 4, 2003, at 1654 Pacific daylight time, a float equipped experimental Schmidt Zodiac 601XL, N819GS, was destroyed when it collided with terrain on Snag Island, Sumner, Washington. The airplane was being operated as a visual flight rules (VFR) local flight under the provisions of 14 CFR Part 91 when the accident occurred. The airline transport pilot-in-command sustained serious injuries and was airlifted to a local trauma center. The airplane was owned and built by the pilot. Visual meteorological conditions prevailed, and no flight plan was filed for the local flight. According to the accident report filed by the pilot, the flight originated from Lake Tapps approximately 5 minutes prior to the accident. In a written statement dated October 17, 2003, the pilot reported that the water takeoff was normal, however, 400 to 500 feet into the climb, the engine quit. The pilot reported that a straight ahead landing was not possible due to boats on the water, and elected to land near a residential street on Snag Island. In a supplemental written statement dated November 10, 2003, the pilot reported that following the engine failure he turned the airplane to the left, approximately 180 degrees, in an effort to reach a suitable area for landing. The statement continues, adding that after completing the turn, the pilot was still unable to reach a suitable landing area and elected to "...stall into the trees." A witness to the accident reported, in part, that the pilot was demonstrating the airplane's takeoff performance off water. The witness stated he followed the airplane, on a jet ski, during its takeoff glide in an effort to mark the actual point of takeoff. A second witness, who was also on a jet ski, reported that shortly after becoming airborne, approximately 100 feet above ground level (AGL), the airplane "...began a very steep right turn." The witness stated that after entering the turn, the airplane pitched down (nose low) and impacted terrain. Inspectors from the FAA Seattle Flight Standards District Office (FSDO) accessed the wreckage on the evening of September 4, and reported that the airplane was located in a residential area near Snag Island Drive. The inspectors reported that damage to the airplane indicated that it impacted terrain in a nose-low attitude. The inspectors reported that the airplane was destroyed by impact forces and a post crash fire. Following the onsite examination of the wreckage, the airplane was moved to an intermediate storage facility in Tacoma, Washington. The airplane was later moved to the pilot's hanger facility located in Puyallup, Washington. On December 18, 2003, representatives from the National Transportation Safety Board and Rotax Aircraft Engines examined the airplane wreckage at the pilot's hangar facility. Thermal and impact damage was noted to the engine and associated engine accessories. The engine's carburetors and ignition system sustained extensive thermal and impact damage. The ignition harness was damaged. Portions of the exhaust tubing and intake tubing were crushed and dented. The crankcase and cylinder assemblies were damaged, however, remained intact. The airplane was equipped with a three bladed (wood) propeller assembly. Blades one and two were sheared off at the propeller root. Blade three was damaged, but remained attached to the hub. Following the visual inspection, the engine was disassembled for further examination. Disassembly and examination of the cylinder assemblies and associated components revealed no evidence of a pre impact mechanical failure. Further examination of the crankcase and internal crankcase components revealed no evidence of oil starvation or internal component failure. On March 26, 2004, the airplane wreckage and associated components were released to the pilot.