the Do 24 ATT was going to perform a "touch and go" display on the lake. The plane slighly rolled to the left, then made a quick 270 degree turn leftwise ("Ringelpietz") and came to a sudden stop within apx two lenghts of the planes lenghts. The crew stated they hit a floatsome and pictures show a hole in the fuselage. The Amphibian plane was towed by boats to a nearby slip and is now on land for further repair and inspection.