I thought that water certainly had an effect on jet engines. It's even in the basic working principle of it. The amount off mass (air) going out of the engine is a direct measure for your thrust. That's why we have a fan that creates 80% of thrust. Hence, if I add water in the compressor (e.g.rain in the air), I have more mass to displace, and thus more thrust created, no?
Of coarse, there is a limit to water as it also cools the flame in the combuster.
Why did 707's and such types have water injection in the past for takeoff power... More thrust, and more cooling for turbine blades. (and a black smoke trail)