In order to study the motion and stresses of ships in rough water, several research committees of the Shipbuilding Reasearch Association of Japan have made a number of experiments on boards for some years. To determine the actual wave profile, the author, as a member, have tested a recording device which can show continuously the wave profile along the ship's outside-wall. The device consists of electric contacts distributed over the outside of the hull. The contacts and lead wires were sticked directly to the shell planks with resin, without any machining or drilling procedure. The outline of this device and some test results are explained in this paper.