A translucent, cylindrical free-floating monster lurks underneath the sea. It has a mouth large enough that it could devour adult humans, if it chooses to do so.

But it doesn't. What could easily seem like a terrifying sea creature is actually a pyrosome, a jet-propelled organism that is often found with hundreds of others in underwater colonies. It's so rare that one writer called it the “unicorn” of the sea.

[pullquote]

“Among many marine-inclined folks -- such as moi -- pyrosomes are like unicorns. Completely improbable, utterly mysterious,” Rebecca Helm writes in a post for Deep Sea News.

One long pyrosome is actually composed of hundreds -- or thousands -- of clones, which then weave their tissues together to form one tube. Helm compares the pyrosome to a cross between the Borg in “Star Trek” and a clone in “Star Wars.”

“And unlike members of the Borg, which are mentally connected, pyrosome members are physically connected -- actually sharing tissues. And while the Borg live in a big scary ship, pyrosomes are the big scary ship,” she explained in the blog post.

According to Helm, the long tube consists of a pointed end and a hole on the other -- perfect for filter feeding. Each pyrosome feasts on little plankton to fill what look like wire baskets. The waste created as a result of the feeding process is pushed out a hollow tube. This action results in a jet-like propulsion system, allowing the long tube to move.

Not the only undersea animal to utilize this propulsion motion (jellyfish, squid and octopus do it as well), pyrosomes are the one of the few to do so in a consistent, albeit slow, manner.

Although these alien-like creatures sometimes grow to be as much as 6-feet wide, they are delicate and fluffy creatures. As noted by a diver in a YouTube video, a pyrosome feels “like an exquisitely soft feather boa.”