The wide part of a river where it nears the sea; fresh and salt water mix WordNet 3.0 & Open English WordNet

An estuary is a partially enclosed coastal body of brackish water with one or more rivers or streams flowing into it, and with a free connection to the open sea. Wikipedia

Semi-enclosed body of water flowing into the sea. Wikipedia Disambiguation

Type of marine and riverine ecosystem Wikidata

Area at the mouth of a river where it broadens into the sea, and where fresh and sea water intermingle to produce brackish water. The estuarine environment is very rich in wildlife, particularly aquatic, but it is very vulnerable to damage as a result of the actions of humans. OmegaWiki