iPhone 7 and iPhone 7 Plus are splash, water and dust resistant and were tested under controlled laboratory conditions with a rating of IP67 under IEC standard 60529. Splash, water and dust resistance are not permanent conditions and resistance might decrease as a result of normal wear. Do not attempt to charge a wet iPhone; refer to the user guide for cleaning and drying instructions. Liquid damage not covered under warranty.
The iPhone 7's IPx7 water resistance rating means that it can withstand being in up to 1 meter of water for 30 minutes in lab conditions.
It's likely that once launched we'll see numerous torture tests that will demonstrate exactly how water resistant the iPhone 7 really is. No matter the outcome you should still avoid getting your iPhone near water because if damaged Apple will likely refuse to repair under warranty.
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