It doesn't matter if you believe in mermaids. She believes in you.
Gene is a rogue-for-hire, using his one-man ship to make a decent living on the flooded Earth. Most of the population has been driven out to Seaplexes--artificial islands glutted with poverty, commercialism, and organized crime. His AI companion, Stitch, does most of the work of their salvage and smuggling jobs. Life is good.