The best option is to replace the keyboard and clean the laptop as detailed below.
As you know water (liquids) and electronics and electricity are not a good mix.
The minerals in the water cause corrosion and the water also provides circuit paths for the electricity which were not in the laptop's operating design and could damage the components. The corrosion process starts immediately and will not stop until it has been thoroughly cleaned away.
First do not turn on your laptop and then you need to with the laptop turned off, remove the battery as soon as possible from the laptop to minimize further damage.
Then you need to completely dis-assemble the rest of the laptop and clean all the affected parts using Isopropyl Alcohol 90%+ (available from most pharmacies) to remove all traces of corrosion and water. Do not use "rubbing alcohol" as in some cases this is only 70% or less and is not as effective. If you do check the label to verify the amount
Here is a link that in general describes the process.
Electronics Water Damage
As always with electronics, especially surface mounted PCBs be gentle when handling and especially when brushing away the corrosion. You do not want to remove any components from the board.
Here is a link to the service manual for your laptop.
It is handy as it shows how to dis-assemble the laptop to gain access to the keyboard and any affected parts. (Although it appears that you don't need it) It is also good in that it gives the part number(s) for the top cover/keyboard, (see p.16-17). This makes it easy to find suppliers for the replacement part as it is easier to replace the keyboard than to try and fix it as you can cause more problems than what you had if you attempt to repair it.
Just search online using the relevant part number only, nothing else, (keyboards are country specific) in the search term, to get results. The part number is also usually printed on the underside of the part as well to confirm which one it is.
Here is an image that shows what I mean. This is for a USA Black cover/keyboard, part #809303-001
(click on image to enlarge for better viewing)
If this process seems too daunting, take your laptop to a reputable, professional laptop repair service experienced in water damage repair and ask for a quote for a repair. If you decide to do this, do it sooner than later.