Strait
It is a channel
A narrow strip of land projecting from the mainland into a sea or lake is called a peninsula.
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
The stretch of water between Arabia and Africa is the Red Sea. It is a narrow sea that connects the Indian Ocean to the Mediterranean Sea.
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
Spurn Head is a unique coastal landform known as a spit. It is a narrow, curved stretch of land that juts out into the sea, formed by the deposition of sediment carried by longshore drift along the coastline.