A buoy for use in reducing the amplitude of waves in water and a system making use of plural buoys to create a floating breakwater. Each buoy is arranged to be constrained, e.g., connected to an anchor, and comprising a body e.g., a cylindrical member having at least one outwardly projecting fin, that is configured to be resonant and impedance matched. The buoy and anchoring approach allows for self-tuning to the changes in the wave spectrum due to the tidal or storm surge induced changes in the water depth. The body of the floating buoy is not limited to circular cylinder, and could be square, hexagonal, triangular, etc. but must have at least one exterior mounted fin.