According to americanoceans.org, “lots of tiny bubbles clustered together along the edge of the tide is sea foam. Thick sea foams are commonly caused by algae blooms. When big algae bloom and die off shore, large amounts of decaying algal materials frequently wash up. As the wave churns up the biological debris, foam develops.” Adds oceanservice.noaa.gov: “Most sea foam is not harmful to humans and is often an indication of a productive ocean ecosystem.”