In this chapter, we learn about the different types of free-diving equipment. First, we're introduced to the "freediver" , a person who dives without a helmet. He's a guy who doesn't wear a helmet because he's afraid he'll get caught in the water and die. The first thing he does when he gets out of the water is breathe in carbon dioxide, the stuff that's in the air around us, and exhale it back into the air. The idea is that when you breathe in, you want to remove the carbon dioxide from your body. The more you breathe, the more you'll want to get rid of it. If you're not careful, you can end up with a lot of carbon dioxide in your system, which can cause you to die. So, the first thing you should do is breathe out a little bit, and then breathe in less. That way, you won't have as much carbon dioxide floating around in your body as you'd have if you were breathing in all the other stuff. The second thing you need to do is not breathe too much, and not too much at all. This is important, because you can't just breathe in and breathe out, you have to breathe out all the time. So basically, you've got to be careful not to breathe in too much and not to exhale too much. The other thing to keep in mind is that if you breathe too heavily, you might end up blacking out, which is when you have too much