Preview at WWDC likely in June, followed by September launch.
iPhone 6s Surprisingly Water Resistant, but Not Waterproof
The first video pits the iPhone 6s Plus against the Galaxy S6 Edge in a small container, under a few inches of water. Each smartphone survived an impressive thirty minutes submerged under water, and appeared to retain their entire functionalities afterwards. As noted by Keaton Keller, the creator of the video and part of the TechSmartt channel, last year the iPhone 6 died after a brief minute facing the same test.
The second video crafts a similar test, but this time compares an iPhone 6s to an iPhone 6s Plus under similar amounts of water as Keller's video. After about an hour, both versions of the new iPhone retained functionality with features like the camera, 3D Touch, and other basic touch screen responses still intact. Zach Straley, the video's creator, followed up a few days later with an update video that showed both iPhones unlocking with Touch ID, having unaltered sound, and with completely functional charging ports and headphone jacks.
Finally, iDeviceHelp posted a video a bit different than the previous two, this time submerging an iPhone 6s Plus into a swimming pool under four feet of water. After one minute, the phone displayed slight touch screen issues, but appeared relatively safe to use. After two full minutes underwater, the device's screen began to fade out, then turned off and refused to reboot a few moments afterwards. A few minutes later, the iPhone 6s Plus grew hotter and hotter, and about two hours later it was completely dead and couldn't be woken up.
Overall, it appears that the iPhone 6s and iPhone 6s Plus have seen measured improvements in water resistance over last year's models, but complete submergence under liquids up to a few feet will still cause the new devices to meet their demise. So while new iPhone 6s and 6s Plus users can rest assured a small amount of rain or other liquid won't immediately harm their device, larger accidents like dropping it into a swimming pool or lake are still cause for concern.
It should be noted that even under a few inches of water, the iPhones didn't come away completely unscathed, Straley noting in his follow-up video that the iPhone 6s in particular saw a slight digital aberration in the form of a diagonal line across the top of the screen. Still, it appears that Apple has made a noticeable attempt to bolster the iPhone's waterproof quality, which may lend early rumors of the "iPhone 7" a small bit of credibility.