NARRATOR: Sharks are big, fast, fierce predators. But in their first year of life, they are surprisingly vulnerable. To stay alive, they can walk out of water, live in rivers, and even eat their siblings, all in the fight to make it as a baby shark. Sharks are formidable hunters that have evolved over 450 million years. They are the most feared creatures in our seas. Great whites, with the power to leap 10 feet into the air. Mako, with speeds of over 45 miles per hour. But baby sharks don't start out this way. In fact, they're a target for predators, including other sharks. Around 80% of some shark species won't make it to adulthood. Adult sharks don't spend any time caring for their newborns. A baby shark is just another item on their menu. Which is why some pregnant sharks, like this one, travel to shallow water to give birth where big predators just can't go. Exactly where sharks are born is largely still a mystery, so this footage of a shark birth is extremely rare. Once born, many sharks remain in the safety of the shallows in areas known as nurseries, like this one, near tropical Orpheus Island on the Great Barrier Reef. [MUSIC PLAYING]