A long, narrow , deep inlet of the sea between hills or mountains
A inlet of the sea or the wide mouth of a river is called a "Bay".
firth
A fjord.
That would be a "fjord," which is a long, narrow sea inlet with steep sides or cliffs, typically formed by glacial erosion. In southern Ireland, these fjords are often a result of Ice Age glaciers shaping the landscape.
A long, narrow, deep inlet of the sea between steep slopes
A long, narrow, deep inlet of the sea between steep slopes is a fiord.Sentence = "I saw a Fiord when I went to the sea side"....
Ria is a long narrow inlet.
river
No, it is a sea inlet with a narrow mouth. This is called a 'gulf' .
A fjord is the long, narrow sea inlet formed by the submergence of a glacially-carved valley. Fjords typically have steep cliffs along their sides and are found in regions where glaciers have sculpted the landscape.
Arm (of the sea) or bay can be used to describe a narrow inlet, although a bay can be up to 24 nautical miles wide.