The iPhone 8 (7s) is reportedly going to include IP68 water resistance, certifying it's less vulnerable to water exposure than the iPhone 7. Apple's current handset is only IP67-certified. This upgrade would put the iPhone in the same class as the Galaxy S7 and likely the S8.
While the IP67 certification means a device is protected against immersion of 15 centimeters and 1 meter, IP68 ensures a device is protected up to 1.5 meters for 30 minutes.
The "6" part of the certification deals with the phone being dustproof.