Lake Illawarra is a coastal lagoon in New South Wales, Australia, about 6 miles (10 kilometers) south of the city of Wollongong, between Port Kembla and Shellharbour (see Lagoon). The lake has an area of about 12 square miles (32 square kilometers) and is fairly shallow. Macquarie Rivulet and Mullet Creek are the main streams flowing into the lake. Windang Island protects the lagoon from the sea. The entrance is frequently closed because of the build-up of sandbanks.