The blue-lined octopus (Hapalochlaena fasciata) is one of three (or perhaps four) species of venomous Blue-ringed octopuses. It is most commonly found around intertidal rocky shores and coastal waters to a depth of 15 metres (49 ft) between southern Queensland and southern New South Wales. Its mantle can grow up to 45 millimetres (1.8 in) in length. It has an appearance of yellow hide with dark blue or black streaks covering the whole body apart from the underside of its arms. The vibrant blue patches appears as a warning on their skin only when they are disturbed. Blue-lined Octopus is majorly well reputed for being one of the dangerous animals in the sea. Blue-lined octopus is one of the most common of several species of blue-ringed octopuses found in Sydney. Their size range from 4.5 cm