K.B.
Try to plan something for after bath time that they would enjoy doing. Switch the focus from the actual bath to what is coming up after they bathe.
When my kids were younger, we often had "backwards night". This is especially helpful after a long summer day. We would first come in from playing and go straight into the tub. They would then put their pajamas on, eat dessert and then dinner. They thought it was so cool to eat dessert in their pjs before dinner.
We also went on "pajama walks" on nice evenings. After bathed and in pjs, my husband and I would put the kids in the stroller and go for a bedtime walk around the neighborhood. They would say goodnight to everything..."goodnight tree, goodnight street... ". It was so cute and a great way to wind down for bed.
A timer also works great. Set a timer and see how long it takes them to finish their bath. Then each night after, try to beat that time. It's scary how easy it is to get the kids to do stuff with just a timer!
One other thing I used to do is just pull the drain in the tub. I let my kids know that when the water is all gone, their bath is over. Sometimes I also put their towels in the dryer so they wanted to get out and wrap up in the warm, cozy towel.
Good luck!