It's big, it's blue, it's where life began and life certainly wouldn't be the same without it: yes, that's right, it's the sea. This week Helen Scales is taking the show underwater to explore her favourite realm. Among the marine menagerie she'll be revisiting the incredible story of squid that see with their entire body, once again be meeting the humming toadfish, which is teaching us a thing or two about making music, and we'll catch up with the colourful clownfish that, just like Nemo, might soon be needing some help finding their way home...