Tom Sutcliffe talks to the historian Michael Wood about the spirit and adventure of the Vikings who travelled all over Europe and as far east as Central Asia. The Vikings sailed close to the coast whenever possible, David Barrie celebrates the invention of the sextant three hundred years ago which made open water navigation and exploration possible. The majority of foreign goods we buy are transported by sea and Rose George charts the murky world of today's international shipping. The mystery and danger of the sea is a recurrent theme in the latest crime novel from the Icelandic writer Yrsa Sigurdadottir.

Producer: Katy Hickman.