Gallery : An Ocean in Motion

If you’ve ever wondered how the sport of surfing gave birth to such an enduring subculture, look at these California waves and wonder no more. The secret to its grip on the American psyche lies in the waves themselves. The rest--the language, the look--is a sideshow.

Ocean waves are not moving water, but invisible bars of energy moving through water. They are produced when wind blows across a stretch of open ocean and transfers its energy to the sea. Once created, swells move with the predictability of billiard balls, abiding by the same principles that govern all waves--sound, seismic, radio.

Like their high-speed counterparts, ocean waves come in different frequencies and amplitudes. They can be focused (by underwater canyons). They diffract (around islands) or refract (off jetties). They decay.

Measured against other waves, ocean waves move at a glacial pace. Where visible light waves hit the eye at about a quadrillion pulses a second, rideable ocean swells reach shore about once every 15 seconds. They are slow enough to see, big enough to ride.

When they hit shallow water, waves break in any number of ways. If the ocean floor is steep, the breaker heaves like a toppling redwood. And if the shore is dimpled or partitioned by a jetty, the wave can go haywire.