I feel your pain
I too had rotator cuff surgery. A bone spur was the culprit in my case and was putting a lot of pressure on my rotator tendon. It did a lot of fraying of the tendon, which was cleaned up during surgery along with the spur being removed. I had the same dilemma as you as I enjoyed a daily swim routine and triathlon training until the pain sidelined me and surgery became inevitable. I was bummed.
As I am sure you know and have been told- slow easy therapy is best. Trust me. To much too soon will put you three steps back in a blink of an eye, and in the water it is very, very easy to push something too far and not realize it. The cool water while very therapeutic can also be a mask to your healing shoulders comfort zone.
After about 2 months post surgery I got in the pool and started my rotator cuff exercises that you would normally do using a band or light weight. These exercises work perfect using the waters resistance instead of using the bands, and it got me in the pool. Working slowly through these exercises actually gave me a new feel for the waters resistance and feel. When strong enough I started to add basic TI drills. Sweet spot for hours and hours. Eventually I developed a balance drill where I would swim lap after lap never using my arms at all. With my arms at my side and comfortably torpedo like I would start on my back and slowly rotate to sweet spot, than rotate to my belly and back to sweet spot on my other side and back to flat back aging. A full 360. I actually swam this drill for about 45 minutes every day and it did wonders for me. I cork screwed my way up and down the pool gaining new sense of body rotation and balance.
Eventually when my shoulder got stronger and my mobility came back I incorporated an easy under switch to this twisting drill. Not only did it do wonders for my sense of core rotation, the easy under switch really help my shoulder recovery. My doctor was absolutely amazed of the mobility I had just after 3 ½ months post surgery. In time I was slowly and gently adding my first strokes back into the drills.
Take this opportunity to get back to basics. It will do wonders in the long run. The down time and consistent slow practice of the basic drills again actually made me a better, more efficient swimmer. 9 months after surgery and I have comfortably and easily shaved 4 strokes off my laps and have more ease and understanding of true balance than ever.
Besides eliminating the pain, having shoulder surgery was the best thing that ever happened to my swimming. Be patient and take it slow and enjoy a healthy recovery. Anthony