Blue-ringed octopuses, comprising the genus Hapalochlaena, are four extremely venomous species of octopus that can be found in shells between rocks and crevices in tide pools and also coral reefs in the Pacific and Indian Oceans, from Japan to Australia. They can be identified by their yellowish skin and characteristic blue and black rings that can change color dramatically when the animals are threatened. They eat small crustaceans, including crabs, hermit crabs, shrimp, and other small sea animals.