If your phone has been submerged then don’t even try to turn it on. Leave it OFF until you get it dried out. DO NOT let it sit in a bag of rice and expect this to dry it out. It may possibly do it but it will take days and it may possibly not work and then you will have wasted valuable time. The best thing you can do is open the phone and blow some canned air all around through the inside of the phone and all over the circuit boards. Gently rub down the circuit traces and all around the chips with a cotton swab saturated with alcohol and then let it dry for several hours. If you are uncomfortable with opening the phone you at the very least must drive the moisture out of it with gentle heat. Set it on a heating pad on low heat for several hours out in open air. Do not keep it in a bag. Let air get to it while it is drying with heat. After several hours try the power button. If no power yet then let it sit on low heat for several more hours or through the night then try it again. If this does not solve the problem then it must be opened and checked for corrosion on the logic board. Don’t wait several days to do this. Act right away before lots of corrosion forms.