Some older concrete and rendered pools may have areas that are drummy (hollow sound when you tap it with a hammer), or areas that are worn away. They can be repaired using a sand / cement mix, Just to Eazy, Davco SMP mixture or any other similar materials designed for water immersion. (Not just weather resistant).
For smaller areas you may prefer to use an epoxy filler. Which ever method is used make sure they are fully cured before applying primer and paint. If you leave the surface unfilled it will be rough and uncomfortable to the touch.
Full details are in the Application Notes, from us.
Not sure, then contact us for specific advice.