There is really not enough information in your question to provide a good answer, but for the purpose of discussion I submit the following observation.
There can be no doubt that water injection, at the appropriate percentages, into the combustion of a turbine engine improves performance by reducing temperatures. Nick, Shawn and I have probably all conducted testing on various engines using water injection and water/methanol (or other combustive additive) injection to improve performance for take-off and or landing. Usually the injection is limited because the water or water/methanol is limited so cannot be used throughout the flight.
One can argue that this intentional water injection creates an artificially higher humidity and it might then be argued that high humidity may improve perfromance. Many pilots believe that engine performance is improved in high humdity (e.g. rain, over-water operations). This does not argue against Nick's statement. In terms of pure air density he is correct, but because the lower engine temperatures during combustion at high engine power settings when water is injected into the engine have a greater impact than lower density during compression in the overall power equation, water injection (high humidity) can improve the performance of some engines.