An embouchure is the mouth of a river, where it meets another body of water such as an ocean or lake. A RIA is a type of river mouth that is formed when the sea floods a river valley. A DELTA is a triangular-shaped area of land that forms at the mouth of a river, where the river splits into several smaller rivers. An ESTUARY is a partially enclosed body of water where fresh water from a river mixes with salt water from the sea. Boca is the Spanish word for river mouth. INFLUX is the flow of water into a river mouth, while OUTLET is the flow of water out of a river mouth.