When the wind is right and the sea is at a certain stage in the cycle of the tides, you get foam. Not just the bubbly stuff that is part of every wave, but great piles of suds, as if an overloaded washing machine has leaked its load, drift up the beach, bouncing and rolling with the breeze in great lumps. They last a surprisingly long time too, accumulating like yellowing special effects from a cheap sci-fi movie.