I would not recommend rice as a solution.
Rice will not remove all of the water (it will just delay the possibility of cleaning the phone properly).
The minerals and electrolytes in the water remain behind after evaporation and WILL cause corrosion which BEGINS IMMEDIATELY and progressively gets worse over time. The sooner you can open the phone and clean out the water and corrosion, the less damage will be caused by corrosion.
At the very least, the phone should be disassembled and the logic board should be cleaned with 99% isopropyl alchohol. Putting the logic board in a professional quality ultrasonic cleaner will complete the removal of corrosion and is highly recommended.
I would recommend replacing the battery as well. I have seen batteries fail spectacularly after water exposure (sometimes weeks or months after). Bulging, heat, smoke, fire!
Even that is not a guarantee for full recovery of the phone. Many times the phone is not fully functional even with best efforts of water damage cleaning.
But don't use rice. If you know someone who did and their phone works, they just got lucky. It didn't fix the problem.
Quoted from the RiceIsForDinner Blog:
Water "damage" is a 3 part problem.
1) Water containing dissolved electrolytes (virtually ALL water and most other liquids) is a liquid conductor of electricity. Once inside the phone, it can wreak havoc on the sensitive electronics because liquids have no shape and can spread into any location, even microscopic crevasses by means of capillary action.
2) Corrosion caused by the water or other liquid containing electrolytes. Most commonly, this is galvanic corrosion and can exist anywhere there are 2 or more metals of varying properties and electricity, though electricity isn't always needed.
3) Board-level problems, ie short circuits and open circuits. An open circuit is when something was short circuited, but became so hot that it failed and the burned out component no longer conducts electricity and the flow of electrons ceases. A short circuit is when electricity is following a pathway that it wasn't designed to follow - the electrons (electricity is the flow of electrons) are taking a short cut to their destination. Both short and open circuits can be difficult to test and locate. In addition, depending on the severity and depth of the problem, they can be expensive to repair, and even exceed the value of the device - at which point, data recovery should be the only reason to proceed.