OK, before people start saying why the hell would you do such a sport. Not the same but similar - I did caving for a big part of my childhood until I was 20. I miss it. The connections you build with the people you do this are very strong, your life depends on it. The places you see are mind blowing - try running into a 60m dive after entering a small hole of maybe 30 cm of diameter, or visiting a room bigger than a stadium at -500m. And there is a certain romance around it - places with names from people that discovered them long ago, places yet to be found, old guys telling gone stories of exploration. Up in the mountains, maybe 1 hour from my old home back in Italy, there is still a search for a special entrance to a big cave system (runs 1 km deep) in order to do explorations also during the winter (a big lake inside the cave closes the "classic" entrance after summer), this search has been going on for 20+ years now, still searching.