The airplane was parked on shore near a dock. The flight instructor (CFI) reported that after starting the engine, the airplane began to move forward, and the wing strut and wing cleared the dock. After the wing cleared the dock, the instructor began to lower the water rudders, and the tail of the airplane began moving toward the dock. A right crosswind was present during the departure from the shore. The instructor reported that full left rudder with the water rudders partially extended was ineffective in stopping the horizontal stabilizer of the airplane from hitting the dock.