S1, E4: This is a journey along Africa's greatest frontier, 29,000 kilometers of coast, from the icy waters of the Cape to the tropical shores of the Indian Ocean. This is a world where seals eat birds, crabs climb trees, penguins live in deserts, baboons eat sharks and seals die of heat stroke. The waters throng with life, from flocks of devil rays to the mighty great white shark, Africa's largest and most powerful predator.