The iPhone 7 comes with an IP67 rating making it splash, dust and water resistant. It also can be submerged for 30 minutes at a depth of one meter, meaning a drop in the sink or bathtub will no longer fry your phone.
However, this isn’t to mean you can take the iPhone for a swim as it isn’t waterproof.
iFixit’s teardown we can see that the phone is more water friendly than its predecessors. There is adhesive throughout the phone, protecting it from water damage and
even gaskets throughout the ports and buttons found on the iPhone 7.
This does make reparability harder, but it’s still possible to change key components, such as the battery. It should be noted that if you intend to repair and open your iPhone 7 (after your warranty has expired), that its water resistance seal will be broken. It will therefore be a trade-off between opening your phone versus losing its water resistant features. Also see:
iPhone 7 Plus review.