Sea Hare
Sea Hares have a secret defence - when threatened, they squirt a bright purple cloud of ink. They probably got the idea from squid, however we’re not convinced the Sea Hare’s defence is quite as effective - when the squid's cloud of black ink clears, the squid is long gone, disappearing with jet propulsion speed. The Sea Hare, on the other hand (rather ironically), can only travel at tortoise speed so has usually only managed to move a few millimetres.
Sea Hares are common in Sydney's intertidal areas. They’re incredibly well camouflaged, but once you spot one you’ll start seeing them everywhere.