If you sit in the back center of the boat and focus on the rider while he's in the middle of the wake your focus will not change no matter where the rider goes. (Pendulum)
I've never shot sequence but I'm guessing that it would work out better if you didn't pan with the shot.
Focus manually or use focus lock and keep the camera pointed at the center of the wake and fire away.
I think it would be easier to stitch the shots together in PhotoShop this way.
I'm just guessing though.