This video gives a pretty good idea.. at least from a UK perspective.
This short video gives some insight into the conditions and rigors facing cave divers John Taylor and Simon Cornhill in their exploration of Bagshawe Resurgence Cave. The limit of exploration is approximately 60m from base which doesn’t sound that far but the underwater passage is tight, awkward and unrelenting, and it takes the divers almost 15 minutes to reach the end. Towards the end of the video there’s a tantalising glimpse of an air surface just beyond an impassable restriction. Simon and John are currently digging and chiselling their way through to this.
See Caving News for more about this project.
[Excerpted from http://www.peakdistrictcaving.info]
I'd rather be diving.. 
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