Here is a Eupentacta quinquesemita or White sea cucumber, feeding with its arms seeking plankton. It was one of several attached to the side of a dock at the boat marina. It appeared to be about 1" long with 3" branching arms.
San Diego County, California, US
Was out of the water for quite some time. It was still alive however.
Picture by Sébastien Stradal.
Echinoderms (Phylum Echinodermata from Greek, ἐχῖνος, echinos – "hedgehog" und δέρμα, derma – "skin") are a phylum of marine animals. The adults are recognizable by their (usually five-point) radial symmetry, and include such well-known animals as starfish, sea urchins, sand dollars, and sea cucumbers. Echinoderms are found at every ocean depth, from the intertidal zone to the abyssal zone. The phylum contains about 7000 living species, making it the second-largest grouping of deuterostomes (a superphylum), after...