About 1" across, on dock. Possibly juvenile Anthopleura sola?
Thanks Ken-Ichi !
This was common on the south side of Moss Landing, though not so common elsewhere.
Note that this particular dock was pretty bereft of life on the underside, and had at least one large male sea lion on the top side, along with numerous signs warning you not to approach the sea lions. The door was open, though. You can park for free along the road, but parking near the more expansive private docks closer to the highway is paid. IMO, head for the north side of the inlet by Kayak Connection, where you also have to pay for parking but there are more options for fouling stuff.
First time seeing this under a 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.