My thoughts would be to seek advice of physical therapist.
When you do pool work, be careful. Sometimes I can feel that I have done something maybe more than my body was ready to do. Start out there with some basic exercising as opposed to doing the crawl stroke or such.
I was doing some research on exercises that help the back on the Internet. There are some good suggestions to begin your movement. You might want to Google that. Most information was repeated so pick what you can do to start.
I would higly recommend to begin with core strengthening as in Pilates, but not all of those exercises at one time. Build up to it. I do Winsor Pilates and the dvd gives an example of someone doing the exercises who cannot perform fully due to that sort of issue. Until you have strengthened you core you should be careful on what you add. Also do go slowly. It will take a good deal of time to get your body into any form to do continuous exercising.
Good luck and Congratulations that you feel well enough to begin moving in a healthy way!
