Mike deGruy and Kate Humble join the international team of scientists and divers as they search for species new to science, and come face to face with the monsters of the deep.

Mike deGruy and the team find extraordinary new species, including a fish that talks and a parasitic catfish notorious for invading the human body; Kate Humble films a rare freshwater dolphin.

The team are halfway through their 3219km-long expedition to film the bizarre creatures that live in the Amazon river. On their journey, they eventually come face-to-face with the giant of the river: the anaconda.

The team of divers and scientists arrive at the very deepest part of the jungle in their search for the creatures of the Amazon river. They soon discover that the overgrown streams contain the richest life, and danger.

It is the climax of the expedition as the team prepare to explore a 100m chasm at the very bottom of the Amazon river. However, they have no idea what lurks within.