Liquids and electronics, especially when the electronics are powered on are not a good mix. (Mobile phones are always powered - the battery supply is never isolated from the systemboard and most liquids are a good conductor of electricity)
The corrosion of the circuitboards caused by the mix of water and electricity, (water alone is bad enough) and the possible damage caused by electrical currents flowing where they shouldn't because of the water will continue until the power has been removed and the corrosion has been removed and stopped by the correct cleaning procedure.
The best thing to do is remove the power as soon as possible and then follow this guide on how to clean the circuitboards. The battery will most probably have to be replaced as well.
Hopefully you may be able to save it.
Electronics Water Damage