Abstract: A device is described for determining the characteristic configuration of long, towed underwater structures such as tubes or cables. The device is a collar which fits around the structure and has sufficient hydrodynamic drag that it remains essentially stationary relative to the linear configuration of the structure as the structure is drawn through it. The device, however, has relatively low mass and assumes the horizontal and vertical position of the structure as the structure is drawn through it. Instrumentation within the device registers the position assumed by the collar and either records it or transmits it to an external receiving station. This information gives a characteristic profile of the elongated structure as it passes through the water.