You might be interested in an article from "Wilderness and Environmental Medicine", 20, 244-249 (2009) called Dead Men Walking: Search and Rescue in US National Parks.

It turns out that hiking accounts for 48% of SAR missions, boating 21%, swimming 6%, and climbing only 5%.

Lots of other interesting information in the article.
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"Toto, I've a feeling we're not in Kansas any more."
-Dorothy, in The Wizard of Oz