On June 25, 2013, at 1300 central daylight time, an Aviat Aircraft model A-1B amphibious airplane, N715SB, was substantially damaged during a water landing on Shagawa Lake, near Ely, Minnesota. The airline transport pilot and his passenger were not injured. The airplane was registered to and operated by a private individual, under the provisions of 14 Code of Federal Regulations Part 91, without a flight plan. Day visual meteorological conditions prevailed for the pleasure flight that departed Ely Municipal Airport (KELO), near Ely, Minnesota, about 1245. The pilot reported that after a short local area flight he began to make water takeoff-and-landings on Shagawa Lake toward the southeast. The pilot reported that his first landing was uneventful and that there were no anomalies with the airplane. He described the lake surface condition as having “light ripples” with a wind speed of less than 5 knots. He stated that his second landing approach and touchdown were again uneventful; however, shortly after the touchdown the airplane began to roll and yaw toward the left until the left wing made contact with the water. The airplane ultimately came to rest partially submerged nose-low in the lake. The fuselage, wings, and amphibious floats were damaged during the accident sequence. An examination of the recovered wreckage was completed by Federal Aviation Administration (FAA) inspectors and an aerospace engineer employed by the amphibious float manufacturer. Their examination revealed substantial damage to several float struts and spreader bars. The left rear float strut attachment fitting with fractured portions of lower airframe longeron tube and the inboard sections of the left and right rear spreader bar mounting tubes were submitted to the National Transportation Safety Board (NTSB) Materials Laboratory for additional examination. The examined components exhibited fracture features that were consistent with overstress. Additionally, no preexisting material defects were noted during the NTSB laboratory examination. The nearest aviation weather reporting station was located at Ely Municipal Airport (KELO), Ely, Minnesota, about 6.25 miles south of the accident site. At 1252, the KELO automated surface observing system reported: wind from 200 degrees at 4 knots, visibility 10 miles, sky clear, temperature 28 degrees Celsius, dew point 12 degrees Celsius, and an altimeter setting of 29.82 inches of mercury.