Growing up in Melbourne we called these crustaceans crayfish, although they are more correctly called rock lobster. Australian coastal waters do not produce the lobsters with large front pincer claws that are known in Europe and America; the nearest relatives we have to these lobsters are the freshwater crayfish - yabbies and marron.
The principal fishing grounds for the southern varieties of rock lobster are off the shores of Tasmania Victoria and South Australia, as well as those culled from Sydney Harbour - in my opinion the best of all. If overcooked, the precious flesh can become quite hard and lose much of its flavour complexity.