Australia’s southern waters contain spectacular and diverse organisms which rival those of tropical reefs in colour and form, though most are not corals. Marine animal communities flourish under low light conditions on deep rocky reefs, caves, crevices, and the undersides of overhangs. Because not much sunlight penetrates to deepwater habitats, they lack the rich plant growth found on shallower reefs. Instead, these communities are dominated by a breathtaking array of free-swimming and permanently attached invertebrate animals. Vertical and overhanging rock walls are covered with delicate lacework bryozoans, soft branching corals, and long thin sea whips. Sponges large and small, in different shapes and colours are abundant in these sponge gardens.