Definitely In Other Waters, an earlier work from the same people who recently brought you Citizen Sleeper. It's a narrative heavy game were you play an AI helping a xenobiologist. You perceive the alien maritime world through a quite minimalistic interface, and nevertheless that game had me on the edge of my seat from the start. Highly recommended, and IMO far too little known.
Currently 70% off and less than 5€. Also available as part of a bundle with Citizen Sleeper.