Footage of giant 20-foot shark surfaces

(CNN)A marine research group has released a video featuring one of the largest sharks they've ever seen, and it's enthralling the web.

The great white shark, nicknamed Deep Blue, is estimated by the conservation group Pelagios Kakunja to be 20 feet long and 50 years old.

Footage of the shark swimming among smaller fish and cages containing observers in 2013 is circulating after it was posted Monday by the group's director, Mauricio Hoyos Padilla, on Facebook.

The video -- which CNN hasn't been able to authenticate -- has drawn more than 2.1 million views.

And big news: researchers believed Deep Blue was pregnant.

Sharks swim closer to the shore to give birth to their pups, which is what researchers have observed Big Blue do, they said in a SlideShare post.

The shark was spotted near Isla Guadalupe, off the coast of Mexico, Hoyos Padilla's Facebook post noted. Pelagios Kakunja is based in the Mexican city of La Paz in Baja California Sur.

The video, titled \"Deep Blue (The biggest shark ever filmed) second part,\" comes after footage was posted in June of the same great white swimming around near a dive master in a diving cage.

\"The dive master was pushing the shark away -- it has a big laceration on the right side,\" Hoyos Padilla told Live Science in June. \"It was really close to the cage, and they have pointy ends. It is so big it couldn't turn properly. So he was trying to push her away, because he didn't want her to get hurt.\"

The film was shot for a 2014 Discovery Channel documentary.

Hoyos Padilla could not be reached for comment for this story.

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