Seagoing Cities — Either the world is entirely water or else the land is simply too dangerous for most humans. Human settlement on this world consists of a number of floating cities that follow the currents and the fish. These city-ships might have been purpose-built for their task, or they could be jury-rigged conglomerations of ships and structures thrown together when the need for seagoing life become apparent to the locals.
Post-Scarcity — The locals have maintained sufficient Mandate-era tech to be effectively post-scarcity in their economic structure. Everyone has all the necessities and most of the desires they can imagine. Conflict now exists over the apportionment of services and terrestrial space, since anything else can be had in abundance. Military goods and items of mass destruction may still be restricted, and there is probably some reason that the locals do not export their vast wealth.