According to the pilot of the Aventura HP experimental light sport aircraft (E-LSA) amphibian airplane, the weather was clear with winds from the southwest at 5 to 10 knots. He stated that after refueling, he departed for a second flight and after 20 minutes, he prepared to land. On an extended downwind leg, at 1,100 feet above ground level (AGL) and about to turn base leg, he encountered some turbulence. He increased power and got out of it, only to enter turbulence again. The airplane went into a dive and at one time he only saw the sky, meaning the airplane was inverted and cutting the fuel flow off to the engine. He was able to regain control and fly the airplane. However, without engine power he was gliding for the woods. The airplane was too close to the trees, and his only option was to reduce airspeed to near stalling and mush down on the treetops. The airplane then started to fall down about 30 feet and stopped with the left wingtip on the ground and the nose 6 feet off the ground. The reported wind, at an airport about 12 miles northwest of the accident site, about the time of the accident, was from 250 degrees at 9 knots.