Mai Tais for the Lost by Mia V. Moss
I absolutely love the world Moss created in Mai Tais for the Lost. All those who could, mostly the rich, have left the surface of Earth for underwater habitats. Life, at least for the lucky, is full of parties, designer drugs, and alcohol. Of course, they also brought with them security/ law enforcement and people to do the menial tasks of life, like cleaning. Marrow Nightingale was once one of the lower classes, but through a quirk of fate, was adopted by the rich and famous Nightingales. She drinks and parties with the upper classes, but isn't at heart one of them. She is, however, the only private detective in Electric Blue Moon and her brother has been murdered.
Marrow is a tough young woman, both overly trusting and cynical. She's definitely an alcoholic and one of those detectives who rub those in authority the wrong way. Mai Tais for the Lost is basically noir with a sci-fi backdrop and...