Also, something to consider, is that the Ring Wraiths had no true physical form. Both fire and water coulod temporarly destroy their "Physical" form. I mean, think about it, why didn't the Wraiths go after the Fellowship? I am currently of the belief that they had to sort of strengthen themselves( i.e. recuoperate
) because Sauron had not yet grown to ful power so neither had they. Just a though.
