1. They are the Borg of the sea.
Pyrosomes are actually colonies composed of hundreds and sometimes thousands of individuals known (reason 1.5 to love pyrosomes) as zooids. The individuals work in unison to propel the colony through the water.
"If the Borg and the Clone Wars had a baby it would be a pyrosome," the marine biologist Rebecca Helm explains.
One long pyrosomes is actually a collection of thousands of clones, with each individual capable of copying itself and adding to the colony. 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. The whole colony is shaped like a giant thimble with a point on one end and an opening on the other, and in some species this opening can be up to 6 feed (2 meters) wide - large enough to fit a full grown human inside.
2. The individual zooids are joined by a "gelatinous tunic."
So how do individual creatures manage to move in such unison? That would be with the help of a, yes, "gelatinous tunic." It joins them all together into a jelly-like body. Ewwwww. And also: ooooooh.
3. They can grow to be up to 60 feet long.
They look, the science journalist Carl Zimmer puts it, like a giant "living wind sock."
4. They belong to a group of ocean-farers known as "pelagic sea squirts."
Pelagic. Sea. Squirts.
5. Scientists refer to them, with only a bit of irony, as "the unicorns of the sea."
They're just so, so weird. Even marine biologists -- people whose job it is to study various deep-sea bizarrenesses -- think so. "Despite their improbable nature," David Bennett puts it, "these horrifying giants, the spawn of the worst movie villains, are actually delicate and fragile. The bizarre unicorns of the sea."