I had a SLAP tear and didn't have surgery. (Natalie Coughlin also tore her laburm and I think rotator cuff and didn't have surgery) LOTS AND LOTS AND LOTS of core work. You can definitely do it - I would suggest taking time off of swimming and just kick while you are rehabbing at least for the first 4-6 weeks. I found that through rehab and tinkering with my stroke to make it more from the core that I was able to come back pain free. You might want to find a knowledgeable coach or PT that knows swimming and have them review your stroke and see what changes can be made to take the pressure off of your shoulder.