At nearly 20 feet in length, with hundreds of razor-sharp teeth and a weight of over 1,300 pounds, the tiger shark is one of the world’s best-equipped predators. Nicknamed the ocean’s garbage disposal for their not-so-picky eating habits, tiger sharks are believed to be solitary animals. This premiere SHARK WEEK program examines an unusual and mysterious event off the South African coast. Each year, tiger sharks gather en masse off Aliwal Shoal and then, as suddenly as they appear, they vanish. South African shark expert Mark Addison, who has worked with tiger sharks for over 20 years, has a theory that these sharks are actually the same individuals year after year -- and he hatches a plan to prove it via satellite tracking. To do so, Addison braves the waters without a shark cage, chain mail suit or scuba gear. He also free-swims without an oxygen tank, to allow him to get up close to tag the sharks with a satellite tracking device -- risking not only being bitten by the tiger sharks, but also drowning.