Immediately open the Air & invert the keyboard, and let it remain for a time such that any remaining water might "fall out". Take it into an Apple Store Genius Bar, ASAP.
The water is not the problem. The problem is everything else dissolved in the water. Minerals, and other dissolved solids make the water conductive. As such it is capable of shorting out every single component within its reach. First to succumb is the keyboard, followed by the logic board, and the battery as the water decends by gravity and capillary action.. Not to mention the potential for corrosion, which will make matters even worse.
Time is of the essence to have the unit serviced, to possibly save components, which if allowed to fail may make the whole unit economically unfeasible to repair.
One of the aspects of any computer is that related connections may exist anywhere in relation to a failed component. e.g. If water has seeped into a ribbon cable for the keyboard, any key(s) may be affected.