The bottom of the Amazon River is home to many of the strangest and fiercest creatures in the world. This is the first in a five-part series following the high adrenaline adventures of a team of divers as they explore and film the depths of the world's greatest river system. It was the first time an expedition had ever attempted anything so ambitious and they discovered an alien world, full of beautiful and bizarre creatures. The darkness also hides many dangers - anaconda, piranha, giant catfish, stingray and caiman. 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.