Waves Most waves are set in motion when friction with wind begins rotating water particles in circular orbits (Figure 11.2). If you were to watch a ball oating on the surface, you would notice that while the wave form moves forward, the ball, and hence the water, does not. On the surface, as water particles reach the highest point in their circular orbits, a wave crest is formed, while particles at their lowest orbital points form wave troughs . Wave height is the vertical distance between the crest and trough of a wave. Beneath the surface in deep water the circular orbits of water particles become progressively smaller with depth. At a depth equal to about half the wavelength (the horizontal distance separating two successive wave crests), the circular motion of water particles becomes negligible. 16. From Figure 11.2, select the letter that identies each of the following. wave crest wavelength wave trough wave base wave height 17. Below what depth would scuba divers have to submerge so that they would not be swayed by surface waves with a wavelength of 24 meters