Here's the deal....coming from someone who has separated both shoulders twice, dislocated both, broke a wrist an elbow in two spots and a shoulder. All in relatively separate incidents...
Sounds like it was a pretty rough break. In terms of those type of injuries, the most important things in my personal experience is #1) rehab, which it sounds like you are doing, range of motion, stretching, strengthening etc..
You gotta get back in the water and you gotta strengthen that sucker back up. Start small like in some flat water or class II or whatever, but make sure that you are warming it up without any unnecessary stress. It will likely hurt like a bitch some and be sore but the more you keep up with the rehab and the more you work to re-strengthen that back up without reversing the progress you have already made the sooner youll be back out there.
I know how it is, good luck out there.
boof to live