A narrow neck of land is called a peninsula. A peninsula is bordered by water on three of its sides.
A narrow neck of land is an isthmus.
Isthmus
The narrow neck of land between Nova Scotia and New Brunswick is called the Chignecto Isthmus.
Isthmus. Booyah...
A narrow neck of land that connects two larger landmasses is called an isthmus. It can be an important geographical feature that may affect trade, transportation, and migration between the connected landmasses.
peninsula
cervix
demijohn
A narrow passage through land is called a gorge.
A narrow strip of land surrounded on 3 sides by water is a peninsula.
A narrow strip of land that connects two larger land masses is called an isthmus. A few examples are Madison Isthmus in Wisconsin, Catalina Isthmus in California, and East Bay Neck in Tasmania.
If you are talking about a piece of narrow land that sticks out into a body of water, then it is called a peninsula.