In the second part of this three-part series, Neil Oliver, Chris Packham, Andy Torbet and Dr Shini Somara join hundreds of archaeologists from around the world who have gathered there to investigate at one of Europe's biggest digs. This week Andy Torbet and some local seafaring volunteers build a boat made of just willow and cow hide, and set out to cross the dangerous Pentland Firth as the ancient Orcadians would have done. Neil Oliver investigates the extraordinary discovery of some human bones, Chris Packham goes in search of whales and Shini Somara uncovers the powers of the tides.