Sea foam seems to show up on the beach at random times but with a little research I found that it is the result of organic matter dissolved in the water. The rough waters break down algal blooms offshore and those proteins and lignins in the water act as foaming agents.
This is a single shot (Nikon D3) and is the -1EV exposure of a five image set. Because there was so much motion in the scene I didn’t want to risk doing a full HDR with ghost removal.