ABOUT NATIONAL GEOGRAPHIC READERS: SHARKS! He's quick. He's silent. He has five rows of deadly teeth. Chomp! Meet the shark-the fish who ruled the deep before dinosaurs roamed the Earth! This fish has soft cartilage so he can glide, twist, and turn before his prey can say "gulp!" He can smell a single drop of blood in 25 million drops of ocean. He can feel electricity given off by his prey. He will lose and replace more than 10,000 teeth in his lifetime. Cool photos bring kids into the shark's world. Fun facts go deep into the shark's scary science.