Transcript for Swimming With Sharks
Through the magic of television, we've kind of made it look like I'm surrounded by sharks. While I am definitely not brave enough for anything like that, you are about to meet a guy who is, even though he was once viciously attacked. Here's ABC's Matt Gutman. Reporter: These are shark infested waters, and Paul de gelder has more reason than most to be afraid. It was 2009, a routine training dive with the Australian Navy when suddenly -- that's de gelder, being pulled under by a ten-foot bull shark. I came face to face with my worst nightmare and it just took me under water and started tearing me to pieces. Reporter: He would lose both his right arm and his right leg. But it's what happened next that is perhaps most shocking. To be honest, I'm just not afraid of sharks anymore. Reporter: De gelder, determined to make sense of the attack, learning more about these predators of the deep, becoming a defender of what almost killed him. They're just trying to exist on our planet and they've been here for much longer than we have. And if we destroy them, that's going to ripple down through the ecosystem onto us and affect our way of life, as well. Reporter: Pointing out we are more dangerous to sharks than they are to us. The predators killing an average of six humans a year, while we kill an estimated 100 million sharks. Swimming with 2,000-pound tiger sharks in the Bahamas, I learned some sharks actually crave affection. De gelder this summer jumping back in, too. For discovery's shark week, all to prove they are as vital to our survival as we are to theirs. Matt Gutman, ABC news, Miami. We should say Paul is right, sharks do deserve protection.
This transcript has been automatically generated and may not be 100% accurate.