We were in Crystal Beach last week. There were lots of tar balls on Wednesday and we actually saw oil in the water. They were pools of oil, but dispersed as the waves hit the beach. We only saw it on Wednesday and we only saw the oil for 15 minutes or so. It was really sad, the waves looked really dark. We never saw oil or tar balls other than Wedneday. It must have moved out of the area. We didn't get in the water after that, but there were lots of other people in the water. Destin was still beautiful and we had a great time. It was a very relaxing vacation. We drove to Seaside one evening and had a great time.
One observation is that they only post the oil signs near the public access, so if you are staying beachfront you may not notice the signs.