I disagree. Thais use tiles and Portland cement to create a waterproof membrane. It's just as effective. You'll lose more water from evaporation.
How do I waterproof my swimming pool?
Waterproofing of the pool is achieved efficiently by applying a strong waterproof cement mortar to the pool's walls and bottom, which acts as a sealing and smoothing layer at the same time. Thus, the smooth, stable and waterproof substrate needed for the application of the epoxy coating is created.