in a utah canyon, a man rappels down a towering cliff but loses control and falls 100 feet to the bottom. >> i thought for sure that my life was coming to an end. >> hey, you okay? >> in the summer of 2009, eric shrever and david cardona are hiking through utah's zion national park. they're both experienced canyoneers, skilled at getting through canyons by any means possible. that includes climbing, rappeling or even swimming. >> i've always loved the outdoors. i've been an avid hiker. but this canyoneering sport, it takes hiking to a whole new level, and i started dabbling in that about three years ago. >> i've been doing canyoneering for about a year with eric. >> this time, david is also going to be a cameraman. >> we thought it would be great to have it on camera and we