@Iluviaporos - I wonder if that means the sharks sensory organ for determining electrical fields in the water works in a kind of electronegative way. I mean, maybe it attracts electrons in order to "see" that there is electricity there.
So, when there is something in the water that is highly electropositive, it overwhelms the shark and disorientates it.
I'm just speculating though. I don't think they have actually figured out how a shark's sensory system works, completely.