C.H.
Have you tried buying colored moose like soap foam,introduce a new bath toy or have his brother and sister take a bath with him? When my daughter was old enough to sit in the bath seat, I had given both of my kids a bath at the same time. They are now 4.5 and 2.5 and I'm sure would be totally bored if only one was to be given a bath. I also have a textured bath tub and I have those stickes and they don't work anywhere as close to those that you can pull off yourself at the end of the bath. It's now the kids job to place those on the side of the bathtub at the end of each bath.
Oh yeah, they also sell colored fizz tablets. I dropped 2 in the other day and when my son realized the water was yellow (there was a lot of bubbles in there before they got in), he started screaming saying that Caitlyn peed in the water and that's why it was yellow. She, of course denied it.
I know a lot of kids don't like taking baths, but if you make it a fun time thing, it will make all the difference in the world. Oh yeah, and we take lots of pictures and see who can have the tallest hat made out of bubbles.