Having enough venom to kill a human, the 'blue-ringed' is what type of sea creature?

Blue-ringed octopuses, comprising the genus Hapalochlaena, are four species of octopus that are found in tide pools and 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 change color dramatically when threatened. They eat small animals, including crabs, hermit crabs, shrimp, and other crustaceans.

They are recognized as one of the world's most venomous marine animals. Despite their small size—12 to 20 cm (5 to 8 in)—and relatively docile nature, they are dangerous to humans if provoked and handled because of their venom which contains the powerful neurotoxin tetrodotoxin.

The blue-ringed octopus, despite its small size, carries enough venom to kill up to twenty-six adult humans within minutes. Their bites are tiny and often painless, with many victims not realizing they have been envenomated until respiratory depression and paralysis start to set in. No blue-ringed octopus antivenom is available yet, making it one of the deadliest reef inhabitants in the ocean.