Where the water spilled is going to be the issue here. Obviously the first thing to do is to wick away any residual water that is visible. I wouldn't mind an owner removing the keyslip (the wood piece that hides the bottom of the front of the keys to wipe up spillage here.)
It doesn't sound like it was in the front of the keyboard. The front of the keys only have key-guides and paper and felt punchings, and key bushings. The bushings are inside the key and the water is unlikely to have spilled "up", the punchings are below the keys and shouldn't affect too much except the key dip.
Further back on the keys is the balance rail. Again, pins poking through the wood of the keys. Water dropped here, might swell the bushings causing sluggishness ... but not dead keys. Back even further is the action. Typically an upright/console action is "out of the way" inside the cabinet unless you've got the front of the piano removed. Or on a grand, tipping water "inward" past the tuning pins (tell me you didn't get them wet) would spill water into the action and cause more havoc since the action is made up of dozens of small parts, pins, felts, machined wood parts, and springs. (Any water on or near the tuning pins needs to be wiped up too.)
If all you've spilled is water, time will dry it out, though regulation may be a little bit off ... probably not enough to worry about. If it's coffee, soda, fruit juice, milk, wine, or something else it's likely that the works are going to be gummed up and will require a technician to examine and regulate the affected parts.
... about the only thing less damaging than a bit of water would be (pure) alcohol. Which may be why Lounge Lizard Pianists keep a brandy snifter on their piano for tips. :--)