The team are on a quest to find a fish that talks and the candiru - a parasitic catfish notorious for invading the human body. Kate heads deep into the jungle to film a rare freshwater dolphin and track down the elusive giant otter.
The team has come to the very deepest part of the jungle, where streams contain the richest life, as well as danger, from four-metre caiman and the electric eel - a fish with a 600 volt shock.
In the climax of the expedition, the team prepares to explore a 100-meter chasm at the very bottom of the river. Underwater robots take cameras down the abyss and find the deep water flesh-feeding candiru.