The light sport aircraft student pilot was taking his experimental light sport seaplane for its second test flight. The student pilot reported that during the landing, he reduced power without verifying the airplane's airspeed and during the landing, the left wing dropped and the airplane touched down hard upon the water. Damage included composite material fractures on both vertical fins. The student pilot had about 32 hours total time and had been signed off by his certified flight instructor to fly a single-engine land light sport airplane. He was not signed off for solo flight in the accident airplane. The student pilot did not report any mechanical malfunctions.