South of Melbourne in Port Phillip Bay, the snorkeling in the Port Phillip Heads Marine National Park is popular for its kelp and sand flats in cool water. In the kelp beds, there is a surprisingly large marine life community. Also, near Sorrento, you may see dolphin and seals.
The most popular site for snorkeling in Port Phillip Bay is called Pope's Eye about 5km northeast of Portsea. It is an artificial reef consisting of bluestone boulders in a semi-circular ring. The water depth is about 1.5m. The marine life includes cuttlefish, featherstars, octopus, various reef fish, and occasionally a seal.
The other popular dive site in Port Phillip Bay is called the Rip. This is a deep wall dive ideal for scuba.
Tip: The Port Phillip Bay snorkeling is known for its cool water, so make sure to take a wet suit.