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