Sea foam is a type of foam created by the agitation of seawater, particularly when it contains higher concentrations of dissolved organic matter, including proteins, detergents, and other pollutants, as well as bits and pieces of organic and artificial matter. Sea foam forms when dissolved organic matter in the ocean is churned up by wind and waves. The creation of sea foam can occur often in gargantuan proportions. Algal blooms are one common source of thick sea foams. When large blooms of algae decay offshore, great amounts of decaying algal matter often wash ashore, and foam forms as this organic matter is churned up by the surf. Sea foam is a global phenomenon, and it varies depending on location and the potential influence of the surrounding marine, freshwater, and/or terrestrial environments.

Most sea foam is not harmful to humans and is often an indication of a productive ocean ecosystem. However, when large harmful algal blooms decay near shore, there is potential for impacts to human health and the environment. During blooms, popping sea foam bubbles are one way that algal toxins become airborne. The resulting aerosol can irritate the eyes of beachgoers and poses a health risk for those with asthma or other respiratory conditions.

Sea foam can be blown by strong onshore winds from the beach face inland. Human activities, such as production, transport, or spillage of petroleum products or detergents, can also contribute to the formation of sea foam.

In summary, sea foam is a type of foam created by the agitation of seawater, particularly when it contains higher concentrations of dissolved organic matter. It is not necessarily toxic, but it can contain pollution or toxins from harmful algae blooms. Most sea foam is harmless to humans and their companions, but it can pose a health risk for those with respiratory conditions during harmful algal blooms.