I caught one just off the break wall at Kurnell as a kid, about 15 years back. I still remember it as if it was yesterday, I just had the hook on the surface of the water and I turned around to grab a new piece of prawn. The hook had just some remains of prawn shell, and suddenly wam, I saw my rod bending like no tomorrow. When I brought it up it was one of the most ugliest looking things, I don't know if it was mutated or something, but it was off-white in colour.
I don't think there are common catch, but they are definetley around.