Underwater

What is deep under water? I think that the bottom of the deep end of the neighborhood swimming pool is pretty deep under water - 12 feet. I read this article yesterday about a guy who set a record for free diving over 100 meters deep on one breath of air!!! What is that he did? Yes, that is what my reaction was.
I just thought that this was a pretty amazing feat and worthy of being shared here at the Human Show.