Social feather duster worm hiding as being approached on a dive in Cancun, Mexico.

Feather Duster Worm Care, Information, & Pictures - Build Your Aquarium

Sabellidae (feather duster worms) are a family of sedentary marine polychaete tube worms in which the head is mostly concealed by feathery branchiae. Sabellids build tubes out of a tough, parchment-like exudate, strengthened with sand and bits of shell. Sabellidae tend to be common in the intertidal zones around the world. Their oldest fossils are known from the Early Jurassic. | Indus Scuba

Outspreading of a feather-duster worm's tentacles to gather food observed | Britannica

Coco Worm Care and Feeding - The Aquarium Adviser

Feather Duster Worm Emerges in Stunning Underwater Display