Any body of water such as rivers, lakes and the ocean has a large amount of plant life growing in it. Just as in a forest, some fraction of this plant life dies and begins to decompose. This breaks the plants down into their constituent lipids, proteins, sugars, etc. These molecules are surface active ... similar to soaps or detergents and this is what causes the foam ... The presence of foam can be completely natural and need not be related to bacteria or pollution.

I have noticed the same foam recently on the Ellwood Beach near where I live.I understand that it comes from naturally-forming organic chemicals that are leeched from decaying plant material in freshwater streams and lakes. When these chemicals are washed into the ocean (maybe by all rain lately) and regularly beaten by the waves, they give the water the strength to hold the bubble-shapes and we see foam. Some artificial chemicals (like soap) could do the same thing, but I believe that in most cases, sea foam is totally natural and harmless. Good news, eh?