Most likely:

* Bay: A body of water partially enclosed by land, typically where a river enters the sea.

Other possibilities:

* Inlet: A narrow body of water that extends into land from a larger body of water, such as a lake or sea.

* Estuary: A partially enclosed body of water where freshwater from a river meets the saltwater of the sea.

* Fjord: A long, narrow inlet with steep sides, formed by glacial erosion.

* Gulf: A large body of water partially enclosed by land, often larger than a bay.

Could you give me more context or a specific example? This would help me determine the best answer!