The Mourning Cuttlefish (Sepia plangon) is a common cuttlefish seen across most sites in Sydney. They can change their colours and body shape rapidly which can be very mesmorising to watch.
They are identified by the blueish tinge below its eye (which gives them their name is that it looks like the cuttlefish is in mourning or crying). It also normally has two darker bands / belts across its body (mantle) and two large blotches at the end of its mantle, like eyes on their back.