Alway do a multilayered approach to water proofing your pool.

I would start by spraying an impregnating waterproofer on the concrete.

If you are going the tile route there are several products that will work. I would put an elastomeric material like hydro ban by Laticrete and then use thier thin set to set your tile on. I would also use an waterproofing admixture in the grout. Make sur you install your isolation joints in the tile with an approved silicone that is rated for submersion.

If you go the plaster route then you can still use the hydro ban and then thin set over it and then plaster. That is an extreme way to do plaster. But remember all concrete including plaster is permeable to water.

Hope this helps.