People do lots of weird things if they can. If they've got the time, the will. And the readies.
No animal on earth would bother to do these things.
Why people would go up the so-called eight-thousanders (the handful of mountains on the planet over 8000 metres) where, basically, the human body is not supposed to be and starts shutting down and moving towards death, is beyond me. You're risking your life at many points, especially on the way down (when your concentration inevitably lessens). I suppose the rush when you reach the summit (if you reach it?) must also be beyond anything I can imagine.
But being in a tin can at the bottom of an enormous pitch black ocean to see a wreck? Personally, I can think of few things more lugubrious. Hey, I love the countryside and walking, but I wouldn't go potholing even for good money. And potholing with a wet suit on and an oxygen tank on my back, making your way through narrow, water-filled tunnels? There is no fucking way…