The class Malacostraca includes all types of crustacean from shrimp, prawns, crabs, lobsters and krill. This page is in development as there are thousands of species and they can be difficult to distinguish by sight. This page contains the several species of Crabs that are often seen in Sydney.
Blue Swimmer Crab (Portunus pelagicus)
This curious crab with a face like something from a horror movie like Predator is quite large and can either be seen hiding in the sand, or out in the open (mostly at night). I have seen this crab mating on many occasions, more so than any other sea creature.