Some key stats -- their venom is in the ballpark of 12,000 times deadlier than cyanide, and despite their size, a single octopus is capable of murdering 26 adult humans in one go. Death takes approximately 90 minutes, and is caused by near-instant paralysis which spreads to the heart and lungs. There is no antivenom, and if you see the rings, you're already dead. Their bite doesn't even really register -- but they don't actually have to even bite you, they can poison the water and kill you just by being close.