3. Blue Ringed Octopus
This octopus is as small as a golf ball. They are very attractive to look at but their venom is enough to kill over 25 adult people. After a bite, the victim will lose their consciousness and eventually die from respiratory failure. As biologists still try to find an antidote for their venom, blue-ringed octopus continues to cause death among divers and swimmers. Victims can often be helped if artificial respiration is provided and maintained before cyanosis and hypotension build up.
