The Point Lonsdale component of the Port Phillip Heads Marine National Park includes spectacular deep water scenery comprising cliffs, caverns, rocky reef walls, sponge gardens and kelp beds.
The Rip side of Point Lonsdale contains an extensive intertidal rocky platform covered with algae such as Neptune's Necklace, and has a number of larger rockpools suitable for snorkelling.
The Point Lonsdale intertidal platform has the highest recorded invertebrate diversity of any calcarenite reef in Victoria.
The reefs offshore from Point Lonsdale provide spectacular underwater terrain with ledges, rock outcrops and bommies, and beds of bull kelp on sections exposed to large waves.
The channel between the main rock platform and the outer reef is around 20 metres wide and 2- 4metres deep and contains a small forest of Giant Kelp, a species which is showing signs of decline along the south east coast of Australia.
The Lonsdale Wall is a series of ledges that mark the edge of the historical course of the Yarra River. The wall drops down a series of ledges from 15 to 90 metres depth, extending horizontally for about a kilometre.
The vertical walls, sheltered caves, ledges and overhangs and their associated communities of colourful sponges, fish and encrusting algae provide spectacular scenery and are popular dive sites. The species diversity in this area is very high, including more than 43 species of fish.
The Kelp Beds are areas with reefs that previously supported Giant Kelp forests and are now dominated by leather kelp. These kelps grow attached to shallow rocky reefs and provides shelter for communities of algae, fish, encrusting sponges, and numerous seastars and sea urchins.
The Sponge Gardens contains a high diversity of sponges and other filter feeding invertebrates in a variety of colours, shapes and forms. Being in the main flow of current through the Rip, these animals are able to extract plankton from the water that passes by. The area derives its name from the spectacular and diverse sponges, branching soft corals, stalked ascidians and carpets of colourful anemones.