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.

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.

Cyril and the team must survive a raging flooded forest and the agonizing sting of one of the jungle's most feared insects on their quest to sample a 200-pound pirarucu. Indigenous villagers help them track down the biggest fish so far but in order to sample the explosive animal, Cyril first has to battle it to shore without getting knocked out by its massive, bony head. To find the hulking piraiba, the crew must journey even deeper into the untamed jungle, where danger lurks around every corner with swarming black piranhas and roaring rapids that can sink their boat in a heart-beat.

It's a battle for survival when a massive piraiba pulls the team down a raging river before they can sample it. Potential disaster greets them at every turn, and the guys are forced to change strategies. Merciless rapids, hidden stingrays, motor failures, lightning strikes, black piranhas and massive falling trees are just some of the dangers the crew must overcome in their quest to sample a giant piraiba for their research. And with a mysterious fish on his line, Cyril gets much more than he bargained for, in a truly dangerous battle.

Their guides abandon the crew in a hostile area and they must now trek on foot into uncharted territory that exposes them to true danger when they cross stingray-infested rapids, run into an ominous poachers camp and face down armed, angry hunters. Their scientific research is at stake, and the guys are forced deeper into the jungle than ever before to find the 200-pound giant piraiba they need to sample. But with a colossal fish finally on his line, Cyril is in for the fight of his life when he gets dragged into a river full of giant black piranhas.