If this refers to Herman Melville's novel, then I don't see what the big deal is. But if it's a porn parody of Herman Melville's novel... then I'm scared.
Well, not to *that* extent... One could imagine all sorts of things: a role-playing game where *she* is Moby Dick and he is the fisherman; or where *he* is a giant albino and is therefore nicknamed Moby Dick. In short, there are no limits to human imagination.