The agitation of sea water, especially when it contains a high degree of dissolved organic material creates foam on the shoreline. The beach is transformed from its normal state (sand, shingles etc) into all covering expanse of tiny bubbles.
It seems that sea foam doe snot have the same appearance or texture – and it can be a dangerous sign of pollutants in the water.
Alga came come from various sources:
- Decomposing or decomposed materials from the seas like plants, animals and excreta
- Chemical waste discharges from Industry
High concentrations of this matter can act as surfactants or foaming agents. Seawater (along with the matter) is churned by waves in the surf zone next to the shore. This process lathers the water and compounds together to make one expansive bubble bath. People need to be careful as such foam may contain dangerous toxins.
Sea Foam – https://en.wikipedia.org/wiki/Sea_foam
What is sea foam – https://oceanservice.noaa.gov/facts/seafoam.html
What is sea foam and how is it recorded – https://www.marineinsight.com/environment/what-is-sea-foam-and-how-it-is-formed/