Water blasting

Just had a quote from a renovator to water blast the coating from my pool. It is a 20'x40' freeform gunite pool with about 2 coats of vinyl based paint that was never applied correctly to begin with. It is blistered in many places and there is chalking. There are some parts that are sound however and seem very durable. The renovator says he can remove this coating with a 7000psi water blaster and guarantees that 90% of the paint will be removed. Does this sound legitimate? I have seen water blasters with very high psi but I do not want concrete damage that these machines might cause.