This crab looks much like the notched shore crab (Paragrapsus quadridentatus). The key differences are the carapace lacks the spots, the legs are slightly thinner and the front of the carapace is more rounded downwards. Apart from this the crab has the single notch behind each of the eyes.

These crabs live in the mud or sand digging borrows in estuaries above the high tide level, these borrows can be interconnecting. Theses crabs can also withstand high levels of pollution so can be found in areas of run off where other crabs cannot be found.
How to identify Helograpsus haswellianus?
What habitats does Helograpsus haswellianus live in?
Can be found under rocks and in burrows at mid to high tide levels
What is the distribution of Helograpsus haswellianus?
South-eastern Australia including around Tasmania
How big does Helograpsus haswellianus grow?
Can grow to around 30mm across the carapace
This does not mean that it cannot be found locally, just that I have not been able to verify records at the time this species was added to the database.
Disclaimer: A lot of work goes into trying to identify and ensure accurate identifications are made and that the listed Descriptions, Sizes, Habitats and Distribution information is as accurate and valid as possible. Unfortunately, information in this arena is ever changing and as such no guarantee can be offered that it is correct or currently valid as a result the information is provided as a guide, and it is always suggested that you do a little research to ensure you have the latest and most accurate information. View the reference's or bibliography I welcome any feedback and comments on the information provided.