I very, very badly want to go spelunking one day. Specifically I need to confront my fear of creepycrawlies first though.
This depends on the water flow in the cave. Plants can't survive any further than daylight reaches, but animals - usually tiny, shrimp-like - are found at the bottom of even very deep caves if o.nly water from surface reaches there, as they are scavenging on organic remains from the surface. Currently the two deepest caves in the world are in Abkhazia - 2200 and 2400 m respectively - and I think these crustaceans have been found there too