I was thinking "why didn't he use the dragon to speed up the trip" and "why didn't he use the rowboat trick to speed up the trip while paused", but figured them out myself.
He said he doesn't want to control the dragon, so turning around right away and asking it to work for him would have been a bit much.
And he's not been afraid of boredom, so probably not that reason for why he didn't drag the ship. But he has been seen to have to eat while paused, so it might just have been that he'd use up too much of the ship's stores. (Risking that more details of his ability gets revealed - people might learn that locking him in is good enough because he'd starve to death.)