My friend Matt Covington researches hydrogeology and geomorphology, with a particular focus on karst aquifers and landforms. This means he spends a lot of time underground. Sometimes waaaayyyyyy underground. And not just on Saturday afternoons, but sometimes for weeks at a time. He has explored some of the deepest caves in the world in Mexico, Peru, Sumatra, Alaska, China, Slovenia and Croatia.
Weeks. Underground. Deep underground. Sometimes scuba diving deep underground so he can go deeper. Places so dark that your body loses its ability to tell night from day, to know when to sleep or be awake.