According to Samsung, the new Galaxy S7 is water-resistant and dustproof to IP68 specification (which means totally dustproof, and water resistant to a depth of 1.5 meters for 30 minutes). This has been accomplished using gaskets and seals, and sticky adhesive that helps keep the water out.
Samsung has also fitted a fine mesh grille over the loudspeaker to keep out liquids, and even waterproofed the headphone and power jacks. The power jack also knows if it has water in it to prevent short-circuiting.
Sounds great, doesn't it? Ideal for those underwater adventures!
Maybe not. Samsung has also kitted the Galaxy S7 out with a couple of moisture-detecting stickers, so if water has been inside the handset, you can kiss your warranty goodbye. Also, there's no water repellant coating on the circuit boards, which means that not only are they vulnerable to short-circuiting, but any moisture that does make its way into the device is free to wreak havoc through corrosion.
Also, while the buttons and SIM tray are protected by gaskets and seals, remember that over time these can wear or get damaged by dirt and debris, which in turn can dramatically reduce the water resistance of the device.
The lack of a water repellant coating on the circuit boards, along with the moisture-detecting stickers, is also worrying to me. If water gets inside the device, then the consequences (all of which are bad) of that are all your problem.
In other words, the added water resistance is nice, but look at it as insurance against accidental exposure to water, nothing more. If the device gets wet, then bad things can still happen to it, and if they do, Samsung will know and wash its hands of any warranty claims (so keep a bag of rice handy!).