If ever there were a sub surface prawn for Grunter, this might be there one. The 'buggy' body and rubber legs will attract attention regardless of water clarity and will suspend naturally when not being retrieved, allowing you to adapt your approach based on the fish behavior.
Although this pattern will sink, we would still opt for a floating line when fishing this fly, unless you need to keep your fly on the bottom, then we'd opt for a full intermediate or intermediate sink tip line.