I would find an internal medicine vet and get a consultation. Ask your vet if s/he knows a good one, they can be a life saver. I know an amazing one in our town who has the best instincts, he's been a lifesaver for my last three dogs, when the vets thought they knew what was going on.
The shaking makes me think of digesitve issues, paarticularly combined with the *new* behaviour with the water. For example, my dog has been having shivering incidents, which we thought was related to her anxiety, but it turn out she is infected with clostridia, which is producing a toxin, and she's a completely different dog when on antibiotics.
Good luck with this, it's awful when you know something I wrong, but can't figure it out.