This is a Lamington Spiny Crayfish. They’re pretty fussy little creatures. They can only live in freshwater streams, at altitudes above 300M, within rainforests or wet eucalypt forests… and there’s not much of that left in Australia.
I spotted this little guy a couple of months back, while hiking through the Springbrook National Park. I think I was happier to see him, than he was to see me.