Divers in Australia have captured rare images of the Pyrostremma spinosum, or pyrosome, sea creature off the coast of Tasmania, Australia.
It is so rare it has been dubbed the 'Unicorn of the Sea' and can grow up to 30 metres long -- the equivalent of two double-decker buses laid end-to-end.
Its hollow, translucent, cylindrical body is made up of thousands of tiny clones called zooids that pull water through its tubes and feed on plankton before pushing the filtered water back out.
Also called a sea squirt, the pyrosomes are classed as pelagic, which means they are free-swimming and live in open water rather than near land.
This means they are rarely spotted and only diving groups are likely to catch a glimpse of the giant creatures.
The long tube consists of a pointed end with a hole on the other that can be as wide as two metres.
Each pyrosome feasts on plankton and according to Rebecca Helm from Deep Sea News, it is a cross between the Borg in 'Star Trek' and a clone in 'Star Wars.'
Helm said: "They're giant, terrifying looking, and trolling through the depths of the ocean, waiting for you to swim in one end and get stuck. Maybe.
"But fortunately, in addition to being slow moving filter feeders, they're also delicate and fluffy."
The pyrosome is so delicate one diver is said to have even described it like a feather boa.
Michael Baron from Eaglehawk Dive Centre recorded the footage of the giant creature off the Tasman Peninsula in Tasmania.
He said it was one of the few areas in the world where a wide range of 'oceanic gelatinous plankton' comes close to shore.