Giant squid, or the Architeuthis, might be the most mysterious beasts in the ocean, if not the world.

In June, a NOAA expedition captured the first footage of a giant squid in American waters.

It comes over 150 years since the first scientific documenting of them. For centuries, people thought they weren't real.

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The Kraken, the mythical beast of the sea, is real.

Giant squid live in the dark depths of the ocean, and very little is known about them to this day.

Most of what the world has learned about the gargantuan creature, which can grow up to 40 feet long and live in a world devoid of sunlight, is taken from their floating carcasses, or from the belly of sperm whales.

Until 2005, no scientist had ever photographed a living giant squid. One hadn't been filmed until 2013. But scientists believe there are millions of them out there.

In June, a NOAA Office of Ocean Exploration and Research expedition captured the first footage of a giant squid in American waters.

The New Yorker's David Grann wrote that giant squid can be "larger than a whale and stronger than an elephant, with a beak that can sever steel cables."

Here's what is known about the mysterious beast, and why so much is still not known.