We just went through this with my 23 month old DD. She LOVED the bath....until she accidentally pooped in it. We didn't make a big deal about it, but we did promptly remove her from the tub so we could drain the water and clean the poop out. She was SO traumatized. She would hyperventilate at the mention of "bath time". It was horrible. I actually did a little research, and apparently this is a normal toddler reaction to pooping in the tub. lol. Upon the suggestion of others who have dealt with this, we purchased "bath crayons". They are non-toxic and are sold in the kids bath aisle. You child can color your tub, and it rinses right off. My daughter loved them. Within about 3 days, she would only whimper at the mention of bath time. Now she likes it again. She still won't sit down in the water, but she will stand there content to color while we pour water over her.
Your child might be a little young for the crayons, but they might work for you. Good luck! Oh, and they also make "bath tablets" that turn the water a fun color. They are non-toxic, too. My DD liked them, but not as much as the crayons.