Humans are just starting to understand the octopus - and it's mind-blowing

Every June 8, folks celebrate the big blue, and to join in on the fun here are some mind-blowing facts about one of the smartest cephalopods in the sea: the octopus!

With their eight arms and giant egg-shaped head, octopuses are one of the most alien-looking creatures on the planet.

Yet scientists have an extremely difficult time studying them in the wild because these highly intelligent invertebrates are the ultimate masters of disguise.

In her book, "Octopus!" Katherine Harmon Courage travels the globe to swim, observe, and even taste some of the many octopuses of the world. Here are 30 mind-blowing facts she learned about this squishy predator of the sea along her epic journey.