I've been fascinated and focused lately on beach/water type scenes. On this one, I thought I'd do a close up of a wave and here it is:
In science, a wave is defined as a transfer of energy. Ocean waves are called mechanical waves because they travel through a medium. The medium in this case is water. The water doesn't actually travel with the wave, but only moves up and down. It's the energy that travels with the wave.
Swells are rolling waves that travel long distances through the ocean. They are not generated by the local wind, but by distant storms. Swells are typically smooth waves, not choppy like wind waves. A swell is measured from the crest (top) to the trough (bottom).