I like your question. Anything called a 'unicorn' is likely to be interesting.

I did a search for 'pyrosomes (unicorn of the sea)'.

Wow - this is exciting! Look at the picture and the news on the link below:
pyrosome

I also like this article:

sea-creatures

This article says that pyrosomes grow up to 60 feet long. The other 11 things in the article are interesting, too.

How about this one?:

news that worry scientists

Pyrosomes aren't actually worms. Pyrosomes are worm-like structures made from a type of tiny marine animal called tunicates that stick together with a gluey stuff like gelatin, and they form a big tube that seawater flows through. The pyrosomes filter out tinier marine animals and plants and eat them. The tunicates that form pyrosomes are called zooids, and each little zooid is a few millimeters long.

The pyrosomes give off light, too - they're bioluminescent.