Western Port Tidal Bay 

Formerly a major river drainage system inundated by the rising sea in the Holocene period, the Western Port sunkland now forms an extensive tidal bay. The waters of Western Port cover an area of 680 square kilometres of which 270 square km, are exposed as mud flats at low tide.

Flora & Fauna - Western Port consists of rocky platforms, sandy beaches and marine habitats. It is home to a diverse range of invertebrates including colonial ascidians, sponges and corals. Mudflats and mangrove swamps around the northern end of the Bay support a large number of invertebrates that are an important food source for waders and visiting migratory birds.

Western Port supports a mosaic of habitat types including underwater seagrass beds, intertidal rock platforms, sandy beaches, intertidal mudflats, tidal channels, saltmarshes and mangroves. The coastline around Phillip Island is of State significance because of its remnant coastal tusssock grasslands and dune scrub, a rare vegetation community in Victoria.