I have a 25K gallon pool that is lined with tradiional plaster. I am not sure how old the plaster is. I can see some, what I would describe as "scuff marks" and I have posted a picture below. My questions is: Do I have to get this plaster redone to avoid a leak or is this just cosmetic. I don't have a good idea as to how thick the plaster is and what additional problems if any, I may be risking if I dont't get his done right away. Also, are there ways to patch this without emptying the pool and redoing all of the plaster. If it is cosmetic only, I may opt to put it off for a while, as it doesn't really bother me. Any insight would be appreciated. Thanks. 
