 Three hundred miles south of the U.S. border, half a million people visit Mexico s Copper Canyon every year -- and over a hundred find themselves in need of rescue.  Four times larger and a thousand feet deeper than the Grand Canyon, starvation and dehydration are big threats for anyone who gets stranded here.  With only a water bottle, a flint and a knife, host Bear Grylls demonstrates how to build a simple compass and climb sheer cliffs safely.  For shelter, he uses ancient caves and makes fire with a traditional "fire saw."  Bear also offers important techniques for finding scorpions or grubs and fishing without a rod or line.