Good call, Steve. That is indeed a prowfish, Zaprora silenus. Prowfish range from Japan to the Arctic (in the Chukchi Sea) and down to southern California, so you were fishing in the heart of their territory. They grow to about 40 inches long (yours is almost maximum size), and the adults live near the bottom in depths ranging from 33 to at least 2,600 feet. Juvenile prowfish always seem to hang around jellyfishes; when frightened, they swim right up inside the bell or shelter near the tentacles. Adults live on reefs, usually in caves, so it sounds like you drifted off the sand and over some rocks. As you note, jellyfishes are a major part of their diet, as are krill, fish larvae, and other small planktonic creatures. Why a big glob of herring and squid attracted one of these fish is a mystery, but maybe it's like me and rhubarb — I know I hate it, but every once in a while, I think, Oh, what the hell? and try some. Lastly, are they good to eat? I can't find anyone who actually has tried one. However, my associate Alexei Orlov informs me that prowfish are occasionally used in surimi by Japanese fishermen who catch them by accident but says there is no market for them in Japan.