It's about being an undine (gondalier) in Neo-Venezia on Mars. It's slice-of-life so nothing really seems to happen except over long periods of time but that doesn't really matter. The show is enjoyable because of the characters, the relaxing atmosphere and the message which maybe boils down to relax and enjoy life. It's sometimes described as a "healing" show.
If all that sounds incredibly boring it might not be your cup of tea but I'd watch at least a few episodes first to see.