The Feather Duster, Sabellastarte giganteus, also known as the Fan Worm, is a marine segmented worm that attaches its calcium-carbonate tube to a rocky or sandy substrate by its base. The worm lives inside this protective tube. They have a feathery crown that peeks out, filtering the water column for food using its specialized tentacles. Their tentacles are completely retractable and can be fascinating to watch open and close.
Very shy, rarely comes out, but pretty