There's a mysterious predator lurking in the depths of Australia's wild Southern Ocean, a beast that savagely devoured a great white shark in front of cinematographer David Riggs 11 years ago. Riggs's obsession to find the killer leads him to an aquatic battle zone that's remained hidden until now. Here, killer whales, colossal squid and great white sharks face off in an underwater coliseum where only the fiercest creatures of the marine world survive.