Growing to over 12 feet long and 1300 pounds, the prehistoric white sturgeon is a true freshwater giant, but because of human activity, its populations are now in decline. Cyril and his crew embark on a dangerous, action-packed mission to help scientists protect them. But to find this massive animal, the team must search the raging mountain rivers and dive beneath their frigid waters, all while avoiding bears, rock slides, freezing temperatures and deadly currents.

An exhausting battle with a colossal white sturgeon pushes Cyril to the limit, but before the team can tag the eight-foot giant, it gives them a giant-sized shock. A freak wind storm then forces the team to put their white sturgeon quest on hold and head far north into the mountains to help protect the sturgeon's main food source: the pacific salmon. In order to find these migrating warrior fish, that can weigh up to 100 pounds, the guys will have to leave civilization behind and survive in one of the most hostile, rugged mountain environments in the world. Out here, hostile terrain, black bears and grizzly bears lurk around every corner.

The crew faces-off with a back-breaking, 200-pound giant in the deep waters of the Pacific Ocean, as they seek to help save the white sturgeon's favourite food; the mighty Pacific salmon. Their mission takes them far out to sea, and deeper into the rugged mountains than they've ever been before. To find these elusive warrior fish, they must brave massive waves, raft down treacherous, frigid rapids, and evade hunting grizzly bears.

Time is running out, and the team must return to the Fraser River to find and tag the 300-pound giant white sturgeon they are looking for. But first, they have to find their way out of the remote wilderness to deliver their salmon samples. Stranded by severe weather, they'll need to survive brutal rapids, rappel down terrifying cliffs, climb a massive glacier, and hike across rugged mountains if they want to succeed. And with a massive prehistoric fish finally on the line, the guys are in for a white-knuckled end to their northern mission.

Two giant fish, one heart-pounding mission in the dangerous Amazon jungle that brings Cyril and the crew face-to-face with armed poachers, ravenous piranhas, hunting caimans, massive anacondas and a terrifying flash flood. Their mission: protecting not one, but two of the most massive freshwater giants on the planet: the armour-plated pirarucu, and the gargantuan Piraiba. These elusive giants are under threat from human activity, and the team must find them in order to collect non-intrusive DNA samples for scientists desperate to conserve them, but the jungle won't make it easy.