The iPhone 7 is not waterproof, but is water resistant. Water resistant means the phone could easily survive a splash of water, or quick dip into water. However, if you drop phone into water it is most likely that water will be inside your phone.
What to do if you think there is water in your phone?
Do not try to turn on your phone. If there is water inside the phone it may seems fine but after a while it may turn off. Due to short circuit, water is worst enemy of electronics. Some people suggested to put your wet phone in rice for couple of days to weeks. According to them, it helped them turning their phone back on.
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