The weird looking crustacean is called Moreton Bay bug, I am not sure if they can be found somewhere else. But boy they sure taste good! Sweet, succulent and springy, they are better than the mantis prawn!
If you come across them, eat them. Loads! But they don't come cheap, about $60/kilo. You'll get about 6 to 10 for a kilo depending on the size. I like them simply grilled!