Although the name Yabby is often used to describe any Australia freshwater crayfish, it most properly belongs to the Cheerax destructor.

Yabbies can live in virtually any body of fresh water, running or still. They burrow into muddy banks and sleep during drought, only to emerge when the rains come. 

Yabbies grow to be about 16cm long in total, with the carapace measuring approximately 7cm.
They are brown, blue, green, or almost red in colour, depending on where they live. Yabbies are found naturally in much of South Western Queensland, central and western New South Wales, the majority of Victoria and the eastern part of South Australia.

An enjoyable way to pass an afternoon is sitting on the edge of a dam with a piece of string with a small piece of meat tied to the end, waiting for a yabby to bite the meat and be caught. While most people take the yabbies home and cook them like little lobsters, I'm afraid we always took them home and put the in an unused aquarium with mud and dam water, and watched them for a week or so, them let them go again.