None of them knew the color of the sky. Their eyes glanced level, and were fastened upon the waves that swept toward them. These waves were of the hue of slate, save for the tops, which were of foaming white, and all of the men know the colors of the sea. The horizon narrowed and widened, and dipped and rose, and at all times its edge was jagged with waves that seemed thrust up in points like rocks.
Many a man ought to have a bath-tub larger than the boat which here rode upon the sea.These waves were most wrongfully and barbarously abrupt and tall, and each froth-top was a problem in small boat navigation...
A seat in this boat was not unlike a seat upon a bucking bronco, and by the same token, a bronco is not much smaller. The craft pranced and reared, and plunged like an animal. As each wave came, and she rose for it, she seemed like a horse making a fence outrageously high. The manner of her scramble over these walls of water is a mystic thing, and, moreover, at the top of them were ordinarily these problems in white water, the foam racing down from the summit of each wave, requiring a new leap and a leap from the air. Then, after scornfully bumping a crest, she would slide and race, and splash down a long incline and arrive bobbing and nodding in front of the next menace.
Stephen Crane from The Open Boat
All you ever wanted to know about waves, straight ahead!