In terms of discoveries waiting to happen, aren't there still limitations on how deep we as humans can explore the ocean? Photography might have some aspects I'm unfamiliar with that allow for it, in which case I guess I know how I'll be spending my next Wikipedia perusal, but in my lifetime I remember a lot of "oh, the pressure would kill you" or "it's simply too dark" as explanations. As for what it'd explain... well, let's leave that to the imagination.