The place I know is not in your area, so instead here is a respected physiotherapist in Cham who might be able to advise you as to what is available in the greater Zug area:
Marco Mouwen http://www.rehapet.ch
As far as I know he does not offer hydrotherapy, but he should know who does in the area. (I have used him for other therapies, btw.) Herr Mouwen is at the MyVets practice one (or 2?) days a week and at his own practice in Birmensdorf the rest of the time - but MyVets in Cham is closer to you.
The place I know of is in the Winterthur area:
Kynofit in Efretikon: http://kynofit.ch/Startseite/
Now, I used to go there a long time ago - 12+ years ago - with Psychocollie. This was back when they first opened, they only had underwater treadmills back then. I believe they have a pool now, but you will need to do due diligence yourself as my experience is outdated.
Do make sure you understand prices - hydrotherapy in Switzerland isn't inexpensive.
Wishing your pooch all the best...