Amazing, this is a crinoid swimming (edited after comments)
Never seen one of these before? You have, but they normally look like this:
Crinoids are a type of echninoderm (also in that taxa: sea stars, sea urchins, and sea cucumbers). They were super popular in the Paleozoic and aren’t nearly as common anymore.
For at least one part of their life cycle, they’re anchored to the seafloor and we normally see them looking like the image above - but most eventually become free swimming as an adult.
Like the more well-known types of echnioderms, a crinoid is basically a mouth surrounded by feeding arms. It’s actually swimming using the movement of those feeding arms! This is actually a pretty efficient adaptation, since the feeding arms catch small particles of food and move them towards the mouth - it’s most likely they can swim and snag food at the same time.
