As compared to a stack, a marine cable requires a larger vortex-interfering device. This is because the density of water is much higher than that of air.

Figure 4.8 : Spoilers used in underwater cables

One such device is the plastic ribbon. If woven into a cable at close intervals (Fig. 4.8), the plastic ribbons effectively prevent the vortex shedding. It has been suggested that the ribbons be one diameter (of the cable) wide, extending four diameters behind the cable and spaced no more than one diameter apart.

Congratulations! You have finished Lecture 4.