Lagoon is a shallow body of water that is partly or completely separated from the open sea. The land that separates a lagoon from the sea may be a coral reef, a sandy ridge called a spit, or a narrow expanse of sand called a barrier island. Lagoons that are formed by barrier islands are found along the east coast of the United States and along the Gulf of Mexico.
Sand and other sediments carried in by ocean tides build up in a lagoon because it is protected from the pounding action of waves. These deposits eventually fill in the lagoon and connect the two stretches of land that it separates.
See also Atoll.
