flooded earth

in the far future where the oceans have overtaken most of the land, society has turned to large ship cities that float above it all. much of the worlds population attempted and failed to escape to mars and other inhabitable planets, with the "mass exodus" event billions of people across the world attempted to flee, only to all be killed in a variety of ways. some made it to mars, but little is known as to how those that made it are surviving.