I find it hard to say whether that is more terrifying or the Sterkfontein accident: cave diver gets lost, finds an exist to a non-submerged part of the cave and waits for rescue, alone and in complete darkness. Until he starves to death after three weeks. Is found a few days too late.

Injun Joe’s death in Tom Sawyer comes to mind. He actually found the exit but it had been sealed shut to prevent more kids from getting lost inside the cave. Starved to death 3cm from freedom. (Apologies for the spoiler if anyone reading this had not read Tom Sawyer!)