The entrance of Port Phillip Bay is a region of extremes, with the bathymetry including a 100 m deep canyon and relatively shallow banks. Water entering or leaving Port Phillip Bay thus flows over areas of greatly varying depths and the result is a highly turbulent flow with large eddies. The area is characterised by very strong tidal-currents and sometimes very rough wave conditions.

Immediately behind the entrance is the Great Sands. The major features of the entrance and Great Sands, including the channels, are shown in Figure 3-5. Due to the size and shallow bathymetry of the area, the sands dampen any wave activity approaching through the entrance and also result in any locally derived wind waves being depth limited.

The open coast bathymetry consists of a low angle sandy substrate with rocky reefs scattered offshore of the cliffed areas.

Little information is available to describe the nature of the seabed and bathymetry, the LADS DEM of the bathymetry is presented in Figure 3-6.

Figure 3-5     Great Sands (Cardno, 2011b)

Figure 3-6     2008 Future Coasts LADS bathymetry DEM (NB. white space offshore indicates data gaps)