Usually air and wind is what causes waves on the ocean. The same wind that cools you on a hot summer day or threatens to blow your baseball cap off as you take a stroll near the water is the very wind that causes waves.
The friction of the air blowing across the surface of the water creates a pulling force on the water and results in motion.
If you've ever been to a small lake or pond, you may have noticed this by observing how calm the water can be when the air is still, and how quickly it can become choppy with waves if the wind picks up.
Of course there are other forces that can cause waves...tidal currents, earthquakes, objects falling into the water...but, generally it is the wind that creates waves.
You can observe air and wind creating waves at home by filling a small cooking pan or small tub with water and then either blowing across it or setting up a small fan to blow across it.
Martha's Vineyard has many beaches and some have bigger waves than others.
Find out why I love the beach on Martha's Vineyard.