(Aliens of the Deep Sea/2010) The octopus is very distinctive; it is has a soft, boneless body, two enormous eyes that take up a quarter of its weight and eight tentacles, of which one is a sex organ. This carnivorous predator can change shape and colour at will, walk on land and sea, and cross through fire. It can grow over five metres long and is amazingly intelligent. They are one of the ocean's most complex creatures and one of its most enigmatic. In this insightful programme, we follow scientists in their efforts to understand how the octopus has evolved to have such intelligence, and also explore its very human traits.