Blue-ringed octopus

The blue-ringed octopus (genus Hapalochlaena) is the most venomous octopus. This small cephalopod mollusc lives in warm, shallow reefs off the coast of Australia, New Guinea, Indonesia, and the Philippines. It has a life span of about two years. As of 2020, four different species have been described and named. Other species likely exist.
Description.
The blue-ringed octopus has distinctive blue rings on its body and on its eight arms. This is its warning colouration, which it shows when attacked. The full warning display is bright yellow with blue rings or lines. It is only about 8 in (20 cm) with the tentacles spread wide. 
Diet.
It eats crabs, shrimp, and small fish. It hides in the reef, then catches prey with its arms, bites it with its tough beak, and kills it by delivering a poison in the saliva. The poison is a neurotoxin (maculotoxin) that is strong enough to kill a human being.