During a cruise by H.M.S. Fleetwood in Scandinavian waters last autumn the opportunity was taken of measuring the intensity of echoes received from the sea, for various wave heights. These echoes are commonly known as sea clutter and the object of the measurements was primarily to provide data on which to design suitable anti-clutter circuits for use in civil marine radars. The results obtained, however, show the need for increasing the radar echoing characteristics of small navigational marks and small boats.