Final answer:
An estuary is a wide area at the mouth of a river where it meets the sea. It is partially cut off from the rest of the ocean due to river mouths or deltas. Estuaries can be referred to as bays, lagoons, or areas of relatively shallow water in a coastal environment.
Step-by-step explanation:
An estuary is a wide area at the mouth of a river where it meets the sea. It is partially cut off from the rest of the ocean due to river mouths or deltas. Estuaries are often triangular-shaped and formed as the waters of a river slow down and split into many channels, depositing sand and silt that has been carried downriver.
Estuaries can also be referred to as bays, lagoons, or areas of relatively shallow water in a coastal environment, separated from the open marine conditions by natural barriers such as sand spits, barrier islands, or coral reefs. They have access to the sea but are partially separated from it.
Estuaries can also be found on the continental shelf, mainly consisting of sand and silt. The energy in estuaries decreases with distance from the shore.