South Africa, on May 5, 2012
Sea foam, ocean foam, beach foam, or spume is a type of foam created by the agitation of seawater, particularly when it contains higher concentrations of dissolved organic matter (including proteins, lignins, and lipids) derived from sources such as the offshore breakdown of algal blooms. These compounds can act as surfactants or foaming agents. As the seawater is churned by breaking waves in the surf zone adjacent to the shore, the presence of these surfactants under these turbulent conditions traps air, forming persistent bubbles which stick to each other through surface tension. Due to its low density and persistence, foam can be blown by strong on-shore winds from the beachface inland onto sidewalks and streets.
This happened in August 2007, when the Australian shoreline at Yamba, north of Sydney
Where polluted stormwater from rivers or drains discharges to the coast, sea foam formed on adjacent beaches can be polluted with viruses and other contaminants,and may have an unpleasant odour.
If crude oil discharged from tankers at sea, or motor oil, sewage and detergents from polluted stormwater are present, the resulting sea foam is even more persistent, and can have a chocolate mousse texture.
Sea foam at Ocean Beach in San Francisco on 3-25-11
If the foam forms from the breakdown of a harmful algal bloom (including those caused by some dinoflagellates and cyanobacteria), direct contact with the foam, or inhalation of aerosols derived the foam as it dries, can cause skin irritations or other respiratory discomfort.
On rare occasions large amounts of sea foam up to several metres thick can accumulate at the coast and constitute a physical hazard to beach users, through concealing large rocks and voids, storm debris and, even sea snakes.
A man surrounded by sea foam investigates the ocean during a nor'easter at Hampton Beach
Two women walk through sea foam and take photos during the Nor'easter at Hampton Beach