Caving – also known as spelunking in the United States and Canada, and potholing in the United Kingdom and Ireland – is the recreational pastime of exploring wild cave systems (as distinguished from show caves). In contrast, speleology is the scientific study of caves and the cave environment. The challenges involved in caving vary according to the cave being visited; in addition to the total absence of light beyond the entrance, negotiating pitches, squeezes, and water hazards can be difficult. Cave diving is a distinct, and more hazardous, sub-speciality undertaken by a small minority of technically proficient cavers.
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BillyScraps 
When I read posts like this it brings home three facts to me – I am fat, I am claustrophobic and people are very varied in their pastimes.
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