Ki 925 customized rhodium gold plated CZ ring affected by water?

The short answer – HAYIR, as long as it IS 925 gümüş. But longer answer – it depends what sort of water (see below).
It is not water which makes your silver change colour, but the chemicals within it.
Örneğin, if you are showering in clean water, then your jewellery should be fine.
If you’re going into the sea, then the salt might affect it – try not to wear your jewellery when swimming (this is also because if the water is cold then your fingers can shrink and you might lose your rings).
If you are swimming in pools then there is likely to be chlorine in the water which will eventually cause some tarnishing on your ring (i.e. you will need to clean it more often). Same thing goes for spas/hot tubs as they have chlorine and hot water.
If worst comes to worst and your jewellery changes colour, it is simple enough to clean – a silver cloth can do wonders!