Why does the sea foam?

Seawater contains dissolved organic matter such as proteins, fats and dead algae cells. These compounds reduce the surface tension of water, much like soap, which allows air bubbles to form and persist. Breaking waves and turbulent surf trap air into this organic-rich water, producing foam. After large algal blooms, huge amounts of organic material can create thick blankets of foam along the coast. Most sea foam is harmless, though in some cases it can concentrate pollutants or harmful algal toxins. The foam is typically white because the bubbles scatter light in all directions.