Photographed above is a section of the tombolo at St Ninian’s Isle.
A tombolo is a sandy isthmus (a narrow piece of land connecting two larger areas). The word tombolo comes from the Italian tombolo, meaning pillow or cushion. A tombolo is formed by waves sweeping sediment together from two sides. Eventually, when enough sediment has built up, the beach shoreline, known as a spit, connects with an island and forms a tombolo (info shamlessly copied from the Wikipedia page about Tombolos).