The new Apple iPhone 7 and 7 Plus also have an IP67 water- and dust-resistance rating, which is great for spills and accidents. However, be aware that the standard Apple one-year warranty does not cover water damage. The AppleCare+ plan does include this coverage, so if you plan to use your iPhone -- against all recommendations -- under the water, then you should definitely purchase the AppleCare+ coverage.
As Apple did with the iPhone 6s and 6s Plus, purchasing an iPhone 7 or 7 Plus through the Apple iPhone Upgrade Program includes the entry fee for AppleCare+. Apple posted a breakdown in fees for your iPhone, as shown in the image below.
Now, let's take a closer look at your new iPhone 7 or 7 Plus with multiple incidents. As you can see, if you break more than the display, including water damage, then it makes perfect sense to purchase AppleCare+. There is a difference in the iPhone 7 and 7 Plus fees without AppleCare+ coverage. Values in parentheses are cumulative costs.
Without AppleCare+ (screen only)
With AppleCare+ protection (screen only)
With AppleCare+ protection
Replace 1st broken device
Replace 2nd broken device
Replace 3rd broken device
It's pretty clear that water damage and other damage -- other than screen damage -- without AppleCare+ means you will likely pay more than the device value with two incidents. The table also shows that it's still less expensive than a new iPhone to purchase AppleCare+ if you break your iPhone three times.
AppleCare+ covers two incidents in the two-year coverage period. If you break your display once and then damage your replacement, you will revert to the out-of-coverage fees for any further incidents. AppleCare+ does not protect you for theft or loss.
Given the expensive initial cost of the iPhone and the parity reached with one screen replacement, I am likely going to purchase AppleCare+ for my phones. The water resistance means I plan to use my iPhone 7 Plus while running and in inclement environmental conditions, so the peace of mind gained from possible damage due to water may be worth the cost of AppleCare+.