An estuary is a semi-enclosed coastal body of water with one or more rivers or streams flowing into it, and with a free connection to the open sea.
Estuaries are often associated with high rates of biological productivity.
The key feature of an estuary is that it is a mixing place for sea water and fresh water to supply fresh water.
A tide is a necessary force to maintain a dynamic relationship at the meeting between the two waters.
In non-tidal seas, rivers naturally form deltas or liman.
In eastern Canada, the Saint Lawrence River widens into the Gulf of Saint Lawrence, the world's largest estuary.
See the following related content on ScienceDaily: