The slimy shipworm was discovered hiding in a shell which as found in the Philippines’ shallow mud bays.
It’s the first time the giant species had been investigated, with very little known about their habitat and biology.
Video shows the moment scientists released the mysterious Kuphus polythalamia species from inside a tusk-like shell.
“I was awestruck when I first saw the sheer immensity of this bizarre animal”
Experts tipped the mud-caked shell upside down to reveal the giant, dark coloured creature in its terrifying glory.
Lead investigator Dr Daniel Distel said: “The shells are fairly common, but we have never had access to the animal living inside.”
The huge creature was found deep in the mud of a shallow lagoon.
Scientists say the giant species are “radically different” from the average shipworm which feasts on wood.
The Kuphus instead feeds off the bacteria found in mud.
Marvin Altamia, a researcher at the marine sciences institute, said: “I was awestruck when I first saw the sheer immensity of this bizarre animal.”
The study’s senior author Dr Margo Haygood added: “Being present for the first encounter of an animal like this is the closest I will ever get to being a 19th century naturalist.
“We suspected the giant shipworm was radically different from other wood-eating shipworms.”
The team will continue to research the fascinating creature and the transition between the normal shipworm and the giant species.