I would not say that this really disperses all fire no matter the amount, I suggest leaving that out. I understand how it can protect you against it, like any substance with mass.
You can cut the second paragraph. The stuff about moving it away from the face is just needless. Your water Aura should also not conduct electricity better than anything else, since even pure water does not do that.
All in all your Aura does not become water, but copies the properties of it, which means its "mass", flowing nature (thanks to that mass) and the weak molecular attraction similar to that of H2O molecules, which makes things "wet".
Last but not least keep in mind that your Aura does not stay invisible to the naked eye once it is transmuted, similar to Killua's electricity and especially since you want your Aura to gain mass it would naturally interact with light and be visible.
If I'm understanding anything wrong about the properties you want your Aura to have, please say so.