The family Aplodactylidae (Seacarp) is a small family of around 5 species in total, within the order of Perciformes. In Sydney the common fish to see is the Rock Cale (Crinodus lophodon) which is often seen perching on rocks near the surface of the water feeding on loose or attached algae.
They are pretty shy and so taking photos of them often results in a mad exodus as they all scurry away.
They can reach about half a metre in length and are grey to blue/black in colour with light spots and markings on their body.