Quite something, isn't it?
We think this is a Branched Dendronotus (Dendronotus venustus). Usually this nudibranch (sea slug) is much darker in the Bodega Bay area. This is our first time seeing such a pale individual.
It was almost transparent, with the pinkish digestive gland showing through, and bright yellow spots everywhere — on the body, the oral tentacles, the rhinophores (sensory organs), and the cerata (branching appendages on the back).
Watch for these beautiful nudibranchs on rocky shores with lots of hydroids.