Back injuries are becoming more common among my mates.
I put my back out wakeboarding and worked to strengthen my core, although I'm not in fighting shape at the moment. Some activities I used a brace but then surfing it may not feel right lying on it.
I used voltaran and the slow release are great and if it keeps you surfing.
You could try sup surfing there are some great boards that work well in the surf. I sup more than I surf as my local beach doesn't get great waves.
Good luck