Portomare

Portomare is a world with very little topside land. During its history people first learned to cable small underwater homes on shallow shelves to make villa colonies. Later, as new technology allowed them to go deeper into the vast ocean, reefs were discovered, huge, hollow caverns remaining from ancient geological shifts. With the right chemicals injected into the tops of the reefs to heat and light them, plants can be grown inside, and colonies moved into the reefs, some only large enough for several hundred, while some can hold several thousand. From this point forward, more people on the planet live underwater in deep reefs than on the surface or in villa colonies.