Robert Llewellyn discovers why submarine movies have gripped us for over a century. He travels along the River Medway to find a beached cold war Russian nuclear sub and then on to the abandoned WW2 German U-boat pens on the French coast, recalling many of the real events that inspired these films. From 20,000 Leagues Under the Sea to Das Boot, Llewellyn discovers that fear - and bravery - is the key, and he also reveals the unique role that Walt Disney played in promoting atomic submarines.