Blacktip reef sharks patrol their territories in coral lagoons and around the edges of reefs. They often swim in water shallow enough that their triangular, black-tipped top fin sticks out above the surface, presenting a classic image of sharks as portrayed in movies and cartoons.But blacktips aren't as menacing as they seem. They're curious about divers in their territory, but they're also wary and easily frightened. These small sharks hunt the abundance of fishes that live on the reefs and try to steer clear of people.