Even lower down of my list of 'things to do...' would be potholing. The thought going underground, squeezing my fat body through little gaps in the rock and not knowing if I would get stuck or lost gives me the creeps.
I guess it depends on the professionalism of the organisation running it. I suspect it still works out safer than flying.
With you on the potholing, wolf... I once crawled through the Cu Chi caves in Vietnam - specially widened for tourists - and it was still really unpleasant.
jno - at least you managed to escape from the caves.
I am in no way an adrenaline junkie and, whilst I understand why people go out of their way to do activities that give them a buzz, I have no desire to try out any of these activities.