peninsula. it is surrounded by water on three sides and by land on one side which is the side it stretches
It is called a cape. A smaller piece might be called a sand spit.
Tributary
straits
Strait
Island
Strait
It is a channel
A narrow stretch of sea between two lager bodies of sea is called a 'strait'. As in the Start of Gibraltar
this is called an Isthmus
Channel
Fjord
It is called the Bering Strait. It is bounded on the west by Russia, the east by Alaska (US) and connects the Bering Sea on the southern end and the Chukchi Sea on the northern end.
The stretch of sea between England and France is called the English Channel.
Any "Long narrow arm of the sea" would be called a FJORD.Hope that helps!
a narrow passage in a sea between two portions of land
The Western Front.
Mouth / delta