Follow Dr. Zeb Hogan on his journey to find the largest freshwater fish in Australia: the freshwater sawfish.

Follow Zeb Hogan as he goes in search of the biggest and oldest of North America's river monsters: the White Sturgeon.

Follow Dr Zeb Hogan on his quest to find what could be the world's largest and most deadly freshwater fish: the giant freshwater stingray.

Aquatic ecologist Dr. Zeb Hogan teams up with kayaking experts to discover what monster fish are lurking beneath the surface in Rio Roosevelt.

They are carp from Asia which can jump 10 feet in the air at the sound of a boat motor, turning a day on the water into a boxing match.

Dr Zeb Hogan travels to the American Midwest in search of the paddlefish, one of the largest, oldest and most bizarre -looking freshwater fish on the planet.

Giant freshwater fish are studied at Khone Falls on the Mekong River in Laos.

Zeb Hogan travels to Spain in search of the invasive Wels catfish -- a monster fish capable of growing more than 8 feet long, eating birds, cats, and, as some legends claim -- even humans! The voracious predator is not native to the region, and biologists fear it could be destroying the local ecosystem.