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Rice only works anecdotally. And then causes other issues unless you use only a pure organic rice. If you use rice that has been dyed, it will leave residue all over your phone, and inside the headphone jack as well as the lightning port.
Rice can't work on an iPhone. It isn't magnetic with water, it has to make direct contact. It won't be able to make direct contact without you opening the phone. Opening the phone and putting rice on it could make the residue issue worse. The rice rumor keeps going because some people's phones work after rice, but they would have done the same in an empty jar as well. It could absorb humidity, but if you're in a humid place already, it won't really work. It could only pull a little bit of water out of the phone through humidity anyways imho.
There is no way anyone could know how bad the water damage is, so no one could really tell you what will and won't fix it. Your best bet is the ultrasonic cleaning mentioned in the quote.