Tiger sharks are washing up dead on the beaches of Western Australia with no sign of attack. Forrest Galante has a theory that deadly sea snakes are turning these apex predators to prey. In the battle of shark against snake, are snakes winning?

Scientists in South America are studying the shark species thought to be responsible for a spike in deadly attacks since 1990. Marine biologist Danni Washington and shark conservationist Paul de Gelder join a team tracking tiger sharks off a pristine tropical archipelago in Brazil.