A Spit is a long, narrow ridge of deposited materials that extends from the mainland into the sea. An example in Brunei is Muara Spit and Kuala Tutong Spit.
When the spit is connected the island to the mainland to form a feature is called the Tombolos.
The long shore drift transports materials along the coast. If there is a sudden change in the direction of the coast, the longshore drift continues to transport the materials in the original direction to the deep sea
As the longshore drift enters the deep water, the materials are deposited. Over time, these materials accumulate above the water to form a spit.
The spit continues to grow with the continuous deposition of materials.