Watch: Mysterious Deep Sea Eel Inflates Jaws Like a Balloon, Astounds Researchers

A team of research scientists has spent nearly four months aboard the Exploration Vessel Nautilus, searching the Pacific Ocean for everything from shipwrecks to meteorites.

But even these seasoned professionals couldn't help but be astounded by the weird and wonderful jaws of a gulper eel recently caught on camera.

Credit: E/V Nautilus

Lurking deep below the sea's surface, this bizarre fish—also known as the pelican eel or the umbrella-mouth gulper—has jaws that inflate and collapse like a balloon.

Researchers captured footage of the strange critter as it swam through the Papahanaumokuakea Marine National Monument in the North Pacific Ocean.

The gulper eel's inflatable mouth quickly unfolds into a massive, rippling sac that can capture larger prey. Then, in a flash, it deflates back down to almost nothing.

As you can hear in the video above, this bizarre process came as a shock to the E/V Nautilus team. "That's a fish? What?" one expedition member said. "That was awesome," added another.

According to the expedition's website, this fish is likely just a juvenile. Adults, it says, can reach lengths of up to 3 feet.

In June, the E/V Nautilus helped a NASA scientist track down several small chunks of what could be a space rock that plunged through the skies back in March. If confirmed, this will be the first time meteorites have been recovered from the ocean. Although they can last for millennia on land, they may degrade in seawater.

This is the fourth annual expedition for the E/V Nautilus. This year it has already explored the U.S. Cascadia margin, parts of Southern California, Washington, the northeast Pacific seamounts, regions near Canada and the waters around Hawaii. In October, the vessel will float from Honolulu to San Francisco, before exploring Monterey Bay and finally the Southern California Borderland region.

Viewers can watch every step of the ocean voyage online and even send questions to the explorers onboard via the Nautilus Live website.

In other marine animal news, staff at the Monterey Bay Aquarium recently captured footage of a superpod of hundreds of dolphins charging through the sea in a feeding frenzy. "There are few things more magical in this world than hundreds of dolphins racing through the wild Monterey Bay on a foggy fall morning," the aquarium posted on Twitter.

Researchers probing the Atacama Trench recently discovered three new species of snailfish living some 5 miles below the surface. Scientist Thomas Linley told Newsweek he was "surprised" by the "amazing" find.