content: Algae is green. It is a photosynthetic organism. There is no such thing as a grey foam algae. This is propaganda.  Turbulent waters like waves crashing on the beach can produce foam naturally when breeding organisms release sperm on mass, or it is contaminated by some other biological factor, but it is never this intense and it is not produced in calm waters.  This has to be caused by large amounts of reactive chemicals producing gasses that are trapped by solvents in the water.