Yes, I am in the middle of PT for rotator cuff injury and believe me my heart goes out!
My situation is exacerbated by a hooked acromion process (think cap of shoulder) that inherently impinges more on the supra...so it was a situation waiting to happen. It has resulted in torn tendon (MRI shows it) and resulting problems.
Doc has just started me on a second round of PT and I have been very pleased with the PT progress as has he. SO I encourage you to stay with it, and who knows what you'll be able to recover? If you are a model patient, you may be back in the water - I say, never say never!
At the same time - I would strongly advise you to put solid principles of body positioning and alignment into place with all of your activities. I believe this may well have been what allowed me to go so long without this injury. I am always conscious during exercise of shoulder-to-hip alignment, shoulder rotation, head positioning, and correct movement through space. Never lift additional weight laterally (out to the side) of your body, and avoid overhead presses with weight, though working in frontal plane is permissible as it does not place the same stress on that fragile shoulder joint.
Pectoral flexibility is important too, as well as strengthening the back muscles not only through exercise but through proper alignment during exercise as well as when walking and throughout day as much as possible, to counter the effects of all of our bad sitting and driving habits!
I hope this helps. I for one am hoping for FULL recover of range (MUCH has been recovered) and am willing to work for it.
Onward! Cheers! You're not alone!