Sometimes there is foam in the wrack. I don’t know how it forms; I guess it happens offshore during big storms. This foam differs from normal sea foam which disperses quickly. This foam sticks together and can form piles or long snakes like this. Sometimes rafts of foam are seen floating just offshore in the breakers. On the beach, foam glides with the breeze, on a thin film of water.
Note: This was originally posted late in 2011. It was one of my earliest posts. On August 23, 2017 I updated the featured image. Since I made the original post I’ve learned more about sea foam. If you want to learn more about it, take a look at Drift Line Foam Could Be Phytoplankton Remains.