From space, Abba appears to be a blue jewel. A water world, it is home to three small continents and multiple volcanic island chains. Some of the volcanoes are dormant, others are still active.
The sea is the center of most people's lives, the diet is high in seafood and fruit. Vegetables and grains are grown in the inland areas of the continents. Fisherfolk and other seafarers are a distinct subculture among the Landsmen.
There is more than one subspecies of humanoid inhabitant of Abba. The Landsmen of Abba are much like humans of other worlds, including our own Earth. Mer-people are humanoid inhabitants of the oceans, adapted to life in the water. Although Mer can spend some time on dry land, they are not suited to it.
Some Mer farm shellfish, bivalves, and edible seaweed, some trade valuables with the land-dwellers. There is a significant amount of prejudice among land dwellers about Mer, including stories of kidnapped men and children. There are Mer that enjoy guiding ships through reefs and there are also Mer that will rescue shipwrecked humans. Some, after being poorly treated by landsmen, will simply let them drown and recover the cargoes. Cargo recovery is a lucrative occupation for Mer, and less dangerous than it is for Landsmen.