How to Catch a Sassy - Cat Goes Fishing: April 2018 Update

Unlike the rest of the fish added in this update, the Sassy can be found just below the depth that the radar shows from the surface near the center of the map. Once you know where they are, they are easy to hook and don&put up much of a fight... But you may wish to clear out the area above them first to avoid your catch getting chomped.