The pilot of the amphibious airplane reported that during the 4th water landing of the flight, during touchdown, "the nose pitched down aggressively" and the airplane nosed over. The pilot further reported that he and the passenger were able to perform an emergency evacuation before the airplane sank. The fuselage sustained substantial damage. During a postaccident interview with the National Transportation Safety Board investigator-in-charge, the pilot reported that boat wake developed in the landing area and the nose of the airplane "may have been a little low" during the landing. According to a police report, the passenger reported that "we misjudged the wave and the plane flipped onto its back." The pilot did not report any mechanical malfunctions or failures with the airplane that would have precluded normal operation.