Each year in the Australian outback, the dry season leaves five top predators- giant stingrays, sawfish, bull sharks, and freshwater and saltwater crocodiles- stranded in waterholes with limited food supplies.

The giant eel is a massive, flesh-eating, wall-climbing, air-absorbing, snakelike fish that can attack like a crocodile and live upwards of 100 years. So, of course, Zeb goes in search of two of the largest species.

The Murray cod can grow up to 6 feet long and weigh more than 250 pounds, and is rumored to eat everything from birds to snakes to possums even its own kind. But humans have been encroaching on the cod's river system, and now these enormous fish are rarely seen in the wild.

Kamchatka, Russia, is one of the wildest and most remote locations on earth and is home to the largest salmon population on the planet but why? Zeb travels to the Far East to explore this salmon paradise.

One of the oldest and most bizarre-looking freshwater fish on the planet can be found in the American Midwest. That's where Dr. Zeb Hogan travels to find the paddlefish.

Dr. Zeb Hogan travels to one of the world's largest waterfalls in Laos, where each year millions of fish climb the falls to spawn.