This 2" Urticina crassicornis or Painted Anemone was the only one I found while looking over the edge of the docks today.
At Cabrillo Beach tide pools.
I think this is a juvenile plumose anemone. There are a few adults of this species on the dock.
Sea anemones are a group of water-dwelling, predatory animals of the order Actiniaria. They are named for the anemone, a terrestrial flower. Sea anemones are classified in the phylum Cnidaria, class Anthozoa, subclass Hexacorallia. Anthozoa often have large polyps that allow for digestion of larger prey and also lack a medusa stage. As cnidarians, sea anemones are related to corals, jellyfish, tube-dwelling anemones, and Hydra.