Atlas

(placeholder name)   Atlas has much more water than land - there's remarkably little land, and it usually isn't very well connected. Most cities are simply built on the water at least partially, or under it, depending on how shallow the water rises there.   There are a variety of people on Atlas, but most are at least somewhat better suited to the large amount of water and resulting conditions. There are several major dividing features between people, such as respiratory systems (breathing in air, water, or both), fishlike and other water-effective features, etc.