Andy McConnell shared a video of a blue-ringed octopus during a recent vacation in the Philippines A man captured himself unknowingly holding the world's deadliest octopus. On Thursday, Dec. 11, ...

A viral beach clip has become a cautionary tale about how quickly a harmless-looking encounter can turn dangerous in tropical waters.

Octopuses have gotten a reputation for being cunning camouflagers and intelligent creatures. But some are known for a more ominous reason: They're deadly. One group — the blue-ringed octopus (genus ...