This rarely seen glass octopus bared all recently — even a view of its innards — when an underwater robot filmed it gracefully soaring through the deep waters of the Central Pacific Ocean.

This story appears in the June 2018 issue of National Geographic magazine.

Although rare, bites can be fatal and immediate medical attention is crucial. The blue ring octopus is a small animal with a lethal secret. Though small, this poisonous creature carries a powerful ...