Oddly enough, I'm thinking Jeeves!fish would be a flounder. They are thin, lay on the floor of the ocean until an eye moves around the body (so Jeeves' is pre-eye migration stage). They see everything and blend into the background, jumping out at the last minute to save the day (eat, whatever)
Re: Bearing in mind the only thing I know about them is that Herrings are red and kippers are tasty.
Black fish, with dignified white spots.