S1, E4: In the final programme of the series, the team explore Britain’s busy southern shores. As one of the world's busiest shipping lanes, the southern seas are littered with wrecks. Outside Poole harbour, the team join an archaeological excavation of a mysterious 17th century ship which is one of the most important underwater discoveries since the Mary Rose. The team also examine how we balance the needs of marine life with those of people when the two come into conflict.