Something catches my eye—only for a moment, but it was there, a glimpse of light in the darkness. I may be a bit unstable, but I can still tell the difference between reality and whatever else is out there. I turn slowly in the direction the light came from, hoping to see it again. If it’s alive, it could be anywhere, but if not, it would be just about… here. Nothing. I turn back, and the water behind my helmet is suddenly illuminated. I freeze—for all I know, this thing could be about to eat me for dinner—but just as suddenly, it is dark again. I look back, and see nothing, again, except a rock lying in the sand. The ocean floor is covered in these things—they’re the only other thing down here besides us.