Personally, I'll keep water away from my Scalextric track... However, there are plenty of hard-core slot rally enthusiasts who use water splashes successfully, as well as flour (snow) and cocoa (gravel/mud). I can only think they spend most of their spare time cleaning and drying out their slot rally cars. Good luck to them! The videos do look fabulous.
The water seems fine on a 12V low-ish current analogue circuit, but I imagine it would short out the electronic components on a digital chip, if the chip got wet. That's what happens to so many smartphones when they get a cup of coffee spilt on them or get dropped down the toilet - the #1 cause of iPhone deaths I believe.