Lightly sand that first coat with 220 sand paper. Did you stain the oak? If you did, be careful not to sand into the stain. You can sand most of the satin off if you didn't stain the wood. You should sand between coats of Spar anyway. This will get rid of bubbles and crap that stick to the urethane. I just finished putting 7 coats of Helmsman on last week. Sanded between every coat.
