Astonishing moment rarely-seen prehistoric shark devours its prey

We still know so little about the wonderful worlds at the bottom of the oceans - but every once in a while, we get a magical glimpse.

That's exactly what happened last weekend when a submarine team of researchers filmed a rarely-spotted prehistoric species of shark at the weekend.

The sixgill shark - which has relatives dating back to 200 million years ago – was captured by a deepsea media company named OceanX at 528 metres below sea level on Saturday.

Footage posted to social media shows the incredible animal - which is the world's largest hexanchoid shark, growing to 16 ft (4.9 m) in length - rolling on the seabed and sending a sand cloud up into the water, much to the onlooking team's amazement.

"Oh wow! My goodness! Look at the width of that thing!" one man behind the camera exclaims as the fish bares her teeth at the lens before gobbling up her prey.

"This is a monster. She is huge," another man replies, as they watch her swim away, leaving only shadows and sand in her midst.

Before they know it, the shark has swum back though, and has come headfirst into the glass-encased craft.

She inspects their camera and the team's onboard spear guns, used for sub-based tagging of creatures, before venturing off once again.

The incredible video was uploaded to Twitter on Saturday by Gavin Naylor, the Director of The Florida Program of Shark Research and Florida Museum at the University of Florida.

In his caption, he wrote: "More footage of six-gill at 528 meters from inside the sub last saturday [sic]. This sequence was taken by Lee Frey, our multi-talented sub pilot/engineer/inventor who designed the solenoid triggered spear guns for sub-based tagging. Thanks again to the entire OceanX team. Amazing."

His post quickly went viral, with more than 30,000 people liking it and almost 9,000 social media users retweeting it.

"I'm just very obsessed with this right now. Everything about it is cool!" wrote @LittleBaardo. He was joined by @Weisrock who put "Holy f’ing s**t. Wow," as well as @thebolt909 who commented saying: "That aint [sic] no normal fish eye. That thing SEES you!"

On Sunday, OceanX announced on Facebook that they - along with partners and scientists from Cape Eleuthera Institute, Florida State University Marine Lab, and Bloomberg Philanthropies Vibrant Oceans Initiative - had become the first to tag a bluntnose sixgill shark from a submersible.

"This is historic for a number of reasons. Dr. Dean Grubbs, the lead scientist on this mission, is the first scientist to ever tag a bluntnose sixgill with a satellite tag, but up until last night had only been able to do so by bringing them up to the surface," they wrote. "Because bluntnose sixgills are a deepsea species, it's hard on them physiologically to be tagged in this way."

"Now that we've proven this method can work for deep sea species like the sixgill, we can unlock the world of leviathan deep-sea dwellers and gain important insights into their movement and behavior."

"It could not have been a tenser mission—this was our last chance, after one dive where the tag bounced off the shark, one dive where no sharks showed up, and one dive where a grouper came and tagged itself instead. Needless to say, the mood on #Alucia right now is ecstatic," continued the post.