What happened
The FAA’s narrative, in sentence case. The FAA writes it in capitals and removes private details.
(-23) The pilot was attempting to troubleshoot a higher than normal cylinder head temperature while in the pattern at Guntersville airport in Guntersville, Alabama. With the wheels still down after takeoff, the pilot decided to land the amphibious aircraft in lake Guntersville. Upon touchdown on the water, the wheels down caused the aircraft to flip over inverted. The aircraft ended upside down on a sandbar resting on the aircraft engine (the engine is on top of the fuselage). The sandbar kept the aircraft from drifting away and also exposed the hull of the aircraft and the landing gear. The pilot was able to get out of the cockpit and get to the surface.
As the FAA filed it
(-23) THE PILOT WAS ATTEMPTING TO TROUBLESHOOT A HIGHER THAN NORMAL CYLINDER HEAD TEMPERATURE WHILE IN THE PATTERN AT GUNTERSVILLE AIRPORT IN GUNTERSVILLE, ALABAMA. WITH THE WHEELS STILL DOWN AFTER TAKEOFF, THE PILOT DECIDED TO LAND THE AMPHIBIOUS AIRCRAFT IN LAKE GUNTERSVILLE. UPON TOUCHDOWN ON THE WATER, THE WHEELS DOWN CAUSED THE AIRCRAFT TO FLIP OVER INVERTED. THE AIRCRAFT ENDED UPSIDE DOWN ON A SANDBAR RESTING ON THE AIRCRAFT ENGINE (THE ENGINE IS ON TOP OF THE FUSELAGE). THE SANDBAR KEPT THE AIRCRAFT FROM DRIFTING AWAY AND ALSO EXPOSED THE HULL OF THE AIRCRAFT AND THE LANDING GEAR. THE PILOT WAS ABLE TO GET OUT OF THE COCKPIT AND GET TO THE SURFACE.