Used to do potholing in Devon as part of school activities, back in the days when they’d let a bunch of school kids do dangerous things. Carbide lamps and no safety gear, like roping together etc when going across crevasses, climbing etc.
I loved it, though was freaky when you get told that sign there down that way is a warning that’s it’s a literal dead end. No way you could turn around or back out and no exit. Were a few bits we did with really tight squeezes and just had to trust the guide that you’d come out somewhere and there’s a way out.
Was muddy, oddly warm, some impressive caves, lakes, weird insects that live in the dark.
I’d never do it now though. The thought of it scares me. Plus I’m not the skinny kid I was and just wouldn’t fit down those holes 😀