Watching too much 'Home & Away'
Yabby is a name given in Australia to two different kinds of crustacean.
A freshwater yabby is a crayfish of the genus Cherax (infraorder Astacidea, family Parastacidae). They are often caught for food. A widespread species is the common yabby, Cherax destructor.
A marine yabby is a ghost shrimp (infraorder Thalassinidea), which lives in deep burrows in the intertidal zone. They are used as bait for fishing, especially in Queensland and northern New South Wales. A common species in south-eastern Australia is the Bass yabby, Trypaea australiensis.