I agree with MT and Preacher...you aren't going to hear a bear coming and I doubt you could out swim a bear.  You MIGHT be able to out maneuver one in the water.  IMO that would be crazier than wading into a group of bears swinging a stout stick ... which many of you know is MY solution.
Encountering a persistent camp robbing bear is fairly rare and dealing with one that would actually be stalking and wanting to eat YOU is less likely than being hit by lightning.  ::)