Ok, I've looked everywhere and every guide says it's in the Ancient Waterway. but they don't actually tell you WHERE in the Ancient Waterway the augment is. like what basement level, section of the map. and I already found out that I screwed over how to do the augments correctly anyway, so I pretty much should just stop playing.
Yeah all I know is that to set Augments, you go into Abilities in the menu, and choose an empty slot.