A popular diving destination, these protected waters are part of an 11-sq-km reserve that supports a healthy marine ecosystem, with flora and marine life flourishing amid underwater grottoes and ancient ruins. To see for yourself, PADI-certified Nettuno Diving runs various underwater activities for all ages and abilities, including snorkelling excursions, beginners' courses, cave dives and immersions off Capri and Li Galli, the islands where the sirens are said to have lived.