This is a feather star swimming off the coast of Japan. Feather stars are crinoids or crinoidea, meaning “Lily-like” in Greek, and thrive in the Indian Ocean up to Japan, as well as in the Atlantic. From Wild Singapore

Feather stars can move about by moving their arms. They crawl over soft sediments, using their arms to drag themselves over the surface, lifting up the central portion of their bodies. Their arms and pinnules have tiny hooks that catch on the surface. They can also swim by thrashing their arms in the water in co-ordinated strokes. However, feather stars usually only crawl or swim to get away from predators. They usually don’t move around very much once they find a good spot to settle on. Feather stars are usually perched on top of tall living or dead hard corals, sponges and other sturdy anchors. Here, they extend their arms into the currents and gather food. 

File under echinoderms, the 600-ish species of crinoids are, of course, related to sea stars. Here are more videos of both.