In reply to JSH:
I'm obviously nowhere near your climbing level, but my experience is that swimming 1km front crawl every week over the past few years has massively reduced the number of soft tissue injuries I suffer, particularly pulled hamstrings, achilles etc.
It's non-weight-bearing, so maybe a kinder form of cardio than running. It's also a great way to get fit to swim in the sea or rivers, which is a lot of fun and comes highly recommended by me!
I did read an article by a Polish high altitude mountaineer (can't remember name) living in Ireland, who was preparing for the ascent of an 8,000m peak. Iirc the main training he was doing involved lots of swimming and not much else, possibly the oxygen deprivation element of front crawl is helpful?
If you start swimming for injury prevention I would suggest mainly doing front crawl, but also throwing the odd set of breast stroke and backstroke.. Good luck