It's no secret that Mark Healey is a thrill seeker. He paddles into and gets barreled on 25-foot waves. He skydives. He has voluntarily, on an island off the coast of Mexico, ridden great white sharks — just grabbed onto their dorsal fins and got towed. So with all of these erratic behaviors, it's easy for us to label Mark as foolish. Dangerous. Oh, Healey? That guy's got a screw loose. But when you hear him talk about diving and sharks in this three-minute clip, you hear someone who is thoughtful, calculated and self-aware. "I have a super busy mind," says Mark, "and the only way for me to really have a moment where I'm just being — I'm not thinking, I'm not turning my wheels — is holding my breath, surrounded by water." Still, it's a bit unnerving watching Mark swim with and pet bull sharks at the bottom of the ocean. Then again, he's spent enough time with sharks to know them, to get past those sinister faces. "What I learn from sharks is don't judge a book by its cover," explains Mark. "Sharks can't change their facial expression. They tell you what they want you to know with their bodies. They always look mean to most people." So maybe the same way we were wrong about Mark being foolish, we were wrong about sharks being mean? Maybe. Why don't you go jump in and find out?