Most modern stones today are used with water. But you have to be careful: some stones need to be watered for a long time before use (and then sometimes can be stored permanently in the water), some should only be watered for a few minutes and then should not remain in the water for longer. And some (like the Belgian Whetstone) only need to be moistened a bit before use ("splash and go"). So always follow the manufacturer's instructions!
And do not freeze wet! And also do not dry lying down (because this is supposed to cause cracks).
Please note:Coated plates and risk of rust with water lubrication
Please be careful with non-coated (continuous) water stones because of Oil contamination. Here, however, the experts are not in complete agreement. Most often you hear that once such a stone was oiled, you can not remove the oil from the binder. So it was never usable again with water (or at least only after weeks of action). The Norton Abrasive company doesn't seem to have a problem with that. My one involuntary attempt went rather slippery.
I would not dress a water stone with an oiled stone either.
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