> "It would have been utterly black. But even with a light and a map of the catacombs, it would have been hard for someone ill-prepared to make it out, because the maps that exist are a maddening, brain-like scrawl. Assuming Masha brought a battery-powered flashlight or lantern down into the depths, it would have died after a few hours, making it harder to continue the search for warmth and water.

If she was lucky, she died quickly from the cold. If it was too warm to freeze, and she was exerting herself trying to survive, dehydration would have become severe in perhaps only two days before the symptoms became debilitating. She would have gotten delirious, convulsed, and slipped irreversibly into a coma around the third day, not that she would have noticed the days passing. She couldn't have lasted more than a week."

Just like, take your shoes off and feel the difference between your foot path and the natural undisturbed gravel or dust. Even in the dark you can still tell what you are stepping on.
Simple solutions to complex problems thread.