At 13 months my first ds absolutely refused to go anywhere near the bathtub that he had previously adored. I have no idea what caused it - it was like a lightswitch flipped on day and he would positively scream if he heard the water running. It lasted a couple of months and then it was like nothing had ever happened and he happily took baths again.
: We did a lot of sponge baths during that two months and he was fine. The only problem was the hair -- which he had ton of. I did have to resort to quick hair washes under the sink every so often, lots of screaming involved but it was quick.