The team travel to West Scotland to investigate the wreck of a ship that may have been part of the Spanish armada. As this is a classic case of rescue archaeology, they are joined by the government's Archaeological Diving Unit, whose director Martin Dean explains why this exercise is so important. An ROV is operated from the surface. Historian Felipe Fernández-Armesto talks about the role played by the weather in the Spanish armada. Pottery specialist Duncan Brown looks at several remarkable finds, including some Maiolica ware. Both Phil and Tony do some diving. With the help of marine archaeologist Mark Lawrence, John uses a magnetometer to survey the seabed.