The Gold Coast Broadwater, also known as Southport Broadwater, Gold Coast Harbour and The Broadwater, is a large shallow estuary of water located in the Gold Coast district of South East Queensland, Australia.he entrance of the Nerang River was at Main Beach in the late 19th century but by the 1980s had moved about 6 kilometres (3.7 mi) northwards. The Seaway was completed in 1986 to stabilise the location of the Nerang River Entrance.