Turn the sound off on this video. Here is a guy "cavern diving" without scuba gear for 16 minutes.
It seems like the biggest risk is that the air-pockets could have bad air. http://www.youtube.com/watch?v=X9CT3fatBpE It is unique that he filmed himself doing this crazy stunt. He did a great job filming himself. Someone could write a good article on free-diving sumps, to explain the safety precautions needed, along with examples of fatalities and why they most likely drowned. I imagine most cavers find even duck-unders intimidating when you have to hold your breath for just 2 seconds. Rule # 1, is take a deep breath, beforehand. Right ? David Locklear
