https://en.wikipedia.org/wiki/Port_Jackson
"#PortJackson is a drowned river valley, or ria. It is 19 km long with an area of 55 km2. The estuary's volume at high tide is 562 million cubic metres. The perimeter of the estuary is 317 kilometres.

According to the Geographical Names Board of New South Wales, Port Jackson is "a harbour which comprises all the waters within an imaginary line joining North Head and South Head. Within this harbour lies North Harbour, Middle Harbour and Sydney Harbour."

Port Jackson extends westward from the single entrance known as Sydney Heads (North and South Heads) and encompasses all tidal waters within North Harbour, Middle Harbour, Sydney Harbour, Darling Harbour, Parramatta River and Lane Cove River."