Hermissenda nudibranch, off the southeast point of Santa Rosa, at about 20 ft depth. Why is this particular area so diverse in life forms? I'm not sure what the red algae in the background is. There may be some motion blur in this image: surge drove the nudibranch's cerrata back and forth across its body as I was shooting. This sort of nudibranch always seems to be glowing from within: thus the "common" name, which I've never heard used: opalescent nudibranch. Its pigments must be fluorescent.