Inspired by the stories of his shipwrecked relatives, Ross heads up to the Royal Navy's historic naval base in the far northerly Orkney Islands, Scapa Flow. Here, Ross and dive supervisor Neil Brock link up with expert local dive guide Emily Turton and head out into the water to dive on Second World War wrecks. Ross and Emily explore a captured German scout ship called the F2 and recover a slew of artefacts that could be linked to Ross's two relatives who died serving in the Royal Navy during the conflict. Ross investigates how Winston Churchill hit upon a revolutionary tactic to defend Scapa Flow from U-boat attacks, as the wreck of the sunken SS Tabarka finally gives up its secrets.