Waves breaking on slopes of different steepnesses.
Depending on a slope’s steepness, waves can break in very different ways. On nearly horizontal beaches, spilling breakers develop. On steeper beaches, plunging breakers, the kind of breakers that form the tunnels that people surf in, form. And on very steep beaches, the breakers don’t actually break, but surge up and down.
This can be seen on the large scale when different beaches are known for different kinds of breakers, and one impressive example are Oahu’s North Shore plunging breakers that my friend Tobi took me and a couple of friends to see in 2010.
More awesome breakers were to be seen on the Big Island a couple of days later:
And of course I have movies of those breakers for you, too, first Oahu and then Big Island: