Salt sea foam

The stygian gloom and the gales are still with us, and the sea looks nothing like the pic I posted yesterday. Rather, it is a grey, turbulent beast, with great curtains of spray whipped off the top of the breaking waves and blown wildly off to dissipate in the wind. Today, walking along the coast road, I was bent into the wind and saw nothing but the road at my feet until I'd had enough and turned my back on the gale. Liberated from the rain that had been pelting my face like lead shot, I was able to look at the surf pounding in on a south-ish gale, and from this comes my question for today:

What do you call the froth left behind on the shore by the receding waves? Like the froth on an abandoned cappuccino, it blows away in little puffs, shredding itself among the rocks. And what causes it? What is it made of?

I would love there to be a romantic, literary sort of word for this - but will settle for science.