This is a theoretical and experimental study of the water wave reflector which is floating and moored. Solving motions and moored floating body among waves by the two-dimensional wave theory is proposed to predict the amplitude of reflected and transmitted wave to easily find the wave-length at which the incident wave is reflected or transmitted completely. This wave-length depends mainly on the spring constant of its mooring system. Hence, adjusting this restoring force, a complete reflector or transmitter is composed for an incident wave of arbitrary wave-length.