In a million years or so, descendants of humans (intelligence comparable to wolves) are driven into caves due to competition with land and resources from descendants from alligators and crocodiles. They stay in the deep parts of the caves, a few hundred feet down, there are some fish who feed on plankton and some fungi as well, but the caves are mostly barren, with water being common. Lets say the humans decide to stay in these caves (or the species gets stuck there) for a few million years (it can be 10 million years to 50, i want long term evolutionary effects) what would happen to them, over millions of years?
I know they would probably lose eyes, but i am also interested in the idea of echolocation (they could develop bigger ears to sense slight sounds) and them developing long fingers to sense their surroundings with, that also function as fishing spears, with maybe a bit of webbing to help swim. What do you think? Feel free to write what you think as well as give commentary on my theories.
Extra thing: The food web and oxygen/carbon/nitrogen cycle does not collapse because there is a species of bacteria in the water that feasts on the bat poop and washed up corpses of animals, and the bacteria also take in carbon and expel oxygen, which allows other organisms to breathe.