I use a laser LED from frozencpu. You can direct the LED and get a cool effect almost as if the water is colored.

Also, here is a TIM chart that I like to use. The last couple entries are the liquid metal stuff, personally I don't use them. The prolimatech stuff is normal TIM and supposed to be pretty good. It can be found also at frozencpu, although they are expensive so if you can find it somewhere else go for it.