Will a bathtub liner get damaged if water leaks behind?

If you have water behind a bathtub liner, it should not cause any damage to the liner itself. The bathtub liner is made out of of either acrylic or PVC. Neither of these materials will be damaged by water getting on them. As long as you remove the water, you should not have to worry about any permanent damage to the bathtub liner. However, there are other serious problems that you might run into if water gets under there. For example, water in a dark place can lead to mold or mildew formation which can lead to health problems.