On July 20, 2015 about 2115 Alaska daylight time, a float equipped, Piper PA-18-150 airplane, N8761C, sustained substantial damage shortly after takeoff from Shannons Pond (0Z3), Dillingham, Alaska. The pilot and passenger were uninjured. The airplane was registered to, and operated by, the private pilot under the provisions of Title 14 Code of Federal Regulations (CFR) Part 91 as a personal flight. Visual meteorological conditions prevailed at the time of the accident, and a visual flight rules (VFR) flight plan was filed. In a statement provided to the National Transportation Safety Board (NTSB) investigator-in-charge (IIC), the pilot stated that during takeoff, after reaching the planned takeoff decision point, full flaps were applied. The airplane immediately became airborne and climbed about 40 feet above ground level (agl).Once reaching that altitude, the airplane did not have the necessary airspeed to continue climbing. In an effort to avoid impacting the trees ahead, a left bank was initiated and the airplane impacted a flat area of muskeg adjacent to Shannons Pond. A post-accident engine exam revealed no mechanical anomalies or malfunctions that would have precluded normal operation. The spark plugs were removed and the propeller was rotated and compression was observed. The closest weather reporting facility is Dillingham Airport, Dillingham, about 3 miles southeast of the accident site. At 2053, an aviation routine weather report (METAR) from the Dillingham Airport was reporting in part: wind from 110 degrees at 7 knots; sky condition, scattered at 8,000 feet agl, scattered at 15,000 agl, broken at 15,000 feet agl; visibility, 30 statute miles; temperature 68 degrees F; dewpoint 52 degrees F; barometric pressure 29.94 inHg.