Sometimes when you go looking for deep-sea corals you find the darnedest things. This is Anthomastus ritteri, a true soft coral (order Alcyonacea) among the octocorals. The images show one colony with polyps retracted (top), and another with polyps extended (bottom).
"The polyps have a strange diurnal pattern of extension and retraction that varies among individuals," says Dr Erik Cordes from Temple University. The polyps are in and out once day, but not synchronized. Cordes made the observation while he maintained the animals alive in cold water aquaria. Here we see the behavior in-situ.
Images are from Sur Canyon in Southern California near 300-400 meters depth. For more like this see the West Coast Shakedown photo album.