Mind-blowing facts about this alien-looking creature that's one of the hardest to study in the wild

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 world 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.