It had four drainage outlets into the Port Phillip Bay, including the modern-day Kananook Creek/Eel Race Drain, Patterson River and Mordialloc Creek (a distributary of the Patterson River's upper section, the Dandenong Creek).
Explorer William Hovell discovered "a very extensive fresh water marsh, from 12 to 15 miles long and 11/2 to 6 broad, and only separated from Port Phillip by a narrow ridge or bank of sand not more than from two hundred to three hundred yards wide.
Due to modern land developments and drainage measures only remnants of the swamp remain, such as the Edithvale-Seaford Wetlands.
The swamp occupied 5260 ha, extending almost from Mordialloc to Frankston, and had a water catchment of 737 sq km.
By the late 1960s, farming activities had just about ceased, and the area became popular with fox and rabbit shooters.