A new generation of spy creatures search the ocean for intelligent life and find ways of thinking that have to be seen to be believed. The most complex spy creature ever built films the owner of the largest brains on the planet - sperm whales. Spy Whale is the same size as a new-born whale calf and is equipped with an array of cameras.

The spy creatures dive into the world of animal emotions by befriending the most complex minds in the ocean and gaining insights into their innermost feelings. Bottlenose dolphins are famed for their intelligence, but Spy Dolphin is on a mission to find out what they really feel.

The spy creatures reveal the extraordinary relationships that exist among the ocean's animals. Spider crabs rise up from the abyss in their thousands to shed their shells, but as Spy Crab discovers, this makes them a target for hunting stingrays.

[Season Finale] The spy creatures explore the challenges ocean life must overcome to survive. Spy Whale is joined by Spy Dolphin as they encounter a humpback whale calf in danger of drowning. Elsewhere, Spy Crab meets the infamous peacock mantis shrimp.