Apple will continue to improve the water and dust proofing on the next generation iPhone. This is according to a report in The Korea Herald, which highlighted the change as one of several "drastic upgrades marking the 10th anniversary" of the iPhone. Current iPhone 7 models are the first smartphones produced by Apple to carry an IP67 rating, keeping dust and water out of sensitive components inside.
Moving to the next level certification increases the depth to which the iPhone can be safely submerged for 30 minutes. Jumping from IP67 to IP68 means the difference between 1 meter (just over 3 feet) and 1.5 meters (almost 5 feet) respectively. Both ratings include a dust rating that means "no ingress of dust" even after 8 hours of exposure to the exterior of the iPhone.
The iPhone 8 will join the Samsung Galaxy S7, which has already achieved an IP68 rating. Both Apple and Samsung are said to be using waterproof tape to keep liquids out while retaining repairability. Glues that have been used to seal out contaminants can make replacing components inside mobile devices more difficult.
Despite Apple marketing the IP67 rating of the iPhone 7, the company has explicitly stated that water damage is not covered under warranty. As devices age, water resistant parts such as gaskets and adhesives can lose their efficacy. The iPhone 7 actually includes a barometric valve inside one of the bottom "speaker" grilles. This feature serves to equalize internal and external pressure, making altitude measurements more accurate.