Tombolo

deposition landform in which an island is connected to the mainland by a sandy isthmus

A tombolo is a line of sand that connects an island to the main land or to another island. They are often shaped like a hammer as they have been created by a complex process, called longshore drift. The word 'tombolo' translates to mound. It is a shaped piece of sand that is attached to something called a spit or bar.

Tombolo near Karystos, Euboea, Greece