On October 25, 2007, about 1300 Pacific daylight time, an amateur-built Ploof SeaRey, N195LS, nosed over during landing at Lake Berryessa, California. The pilot/owner was operating the experimental airplane under the provisions of 14 CFR Part 91. The sport pilot and one passenger sustained minor injuries; the airplane sustained substantial damage. The personal flight departed Yolo County Airport, Davis/Woodland/Winters, California, about 1230, with a planned destination of Lake Berryessa. Visual meteorological conditions prevailed, and no flight plan had been filed. During a telephone interview with the National Transportation Safety Board investigator, the pilot stated he conducted a normal approach for landing on Lake Berryessa. He configured the airplane with the landing gear up and the flaps set down 20 degrees for the water landing. While decelerating the airplane after landing, he heard a loud noise. The airplane nosed over and came to rest floating on its back. The pilot opined there was a submerged object, which caused the airplane to nose over. The pilot reported no preimpact mechanical malfunctions or failures with the airframe or engine. The airplane sustained damage to the hull and right wing.