A frame on the wall, in the dark. Don't turn off the power... it's an aquarium view, and whatever is inside there needs bubbles from an electric blower, and certainly can't call for help if the lights go out and the oxygen stops. Another theory... the only light here comes from the expulsion (or is that explosion) of these oxygen bubbles, exhaled by some creature hidden in the dark, attempting to speak to us from underwater. Maybe the bubbles are leaking to us from another world, equally dark but under greater pressure. Perhaps a change of conditions has allowed the dead dissolved in the ether to precipitate out as bubbles.