The long, baseball bat-sized shells of the giant shipworm (Kuphus polythalamia) have made the existence of these mysterious sea creatures impossible to miss, but this is the first time that scientists have ever laid eyes on their live, oozy interior bodies before.

It turns out, they are even more macabre and alien-like than anyone could have imagined.

“It’s like finding the lost elephant graveyard or finding a dinosaur wandering around, live,” Dr. Daniel Distel, a microbiologist at Northeastern University, told the New York Times.

The first thing that's important to know about the giant shipworm is that it's not actually a worm. It's a mollusk, related to other bivalves, like clams, oysters and mussels. They are the longest bivalves in the world, with shells that can measure 3 feet in length. One of the reasons they're so elusive is that they never peer out of their shells (in fact, their shells are eerily referred to as "crypts"), and they live entirely off the hydrogen sulphide gas produced by the mud that they burrow in.

They might as well be from another planet. One of their more unique features is their gunpowder-black colored bodies, which is unlike other types of bivalves that have white, beige or pink flesh.

"It was pretty spectacular to lift that tube out of its container for the first time. To see this giant gun-metal black specimen was amazing," explained Distel to the Washington Post. "On the one hand, I was pretty excited to see what it looked like inside. On the other hand it was a little intimidating to dissect this incredibly rare specimen."

The researchers knew they had a special opportunity to examine a live specimen for the first time after being cued by a local fisherman to a small population of the creatures living at the bottom of a remote lagoon in the Philippines. Several of the shipworms were transported to the lab inside specialized, elongated aquariums.

You can watch the animal get squeezed from its shell while still alive in the following video. But beware, you may never consume oysters or clams the same way again after seeing it: