Below:

-- Maybe the trapped cavers survive by eating blind cave fish. Maybe it’s a wholly undiscovered species—a species unique to this cave system that they drive to extinction by eating them. One of them comments that he feels like Gollum eating raw fish in the dark.

-- Maybe, before they discover the underground lake with the cave fish, they were forced to eat one of their fallen comrades.

-- The voice recorders are voice activated so the cavers don’t have to remember to turn them on. They use less batteries than video cameras and lights.

-- The cavers, without light or visual stimulation or any concept of time, begin to hallucinate.

-- Maybe there’s a female who’s been harassed by one of her teammates. She would hear movement outside her tent, feel furtive gropings in the dark, whispers in her ear. She doesn’t know who is doing it.

-- Maybe there are Russian scientists who are studying how the radioactive waste in the caves is effecting the ecosystem. They are also studying how it effects political prisoners the Russian government has imprisoned in the caves. The lost expedition finds the scientists in their observation chambers. They can’t get any answers out of the scientists; a struggle ensues, leaving only one survivor: the woman above.

-- Maybe the Russian Army officer who introduces and closes each episode with an overview of the recordings featured, reveals in the final episode that one member of the expedition has escaped through the scientists’ chambers and is probably out there, right now, telling the whole tale to the American embassy.

-- Maybe the woman survives because, as a vegetarian, she refused to eat any cave fish. The fish turned out to be radioactive, poisoning everyone who did eat them.