I found a good spot that doesn't take too much luck. In Fontaine Futuristics there is the Fake Lab. If you set up 2 or 3 turrets in the observation room and then another on a bench in the room. Then just hide in the back and keep zapping the water until you're done.
BTW if you can't get in the room, it's on the top floor you go through a hole in the wall...