Waterproof or Nah?
According to Apple the iPhone 7 is water-resistant, not waterproof. Many think there is not a difference, but this is an important distinction. The iPhone 7 has an official IP67 rating, which refers to dust and water-resistance. The "6" refers to the dust and this is the highest level of protection for that component . Now, the "7" refers to the water-resistance, which isn't the highest level of protection, "9" is, but the "7" will allow an iPhone 7 device to be fully submerged in one meter of water for roughly 30 minutes.
Not so Fast
Now, we know this is exciting news, however, you should not ever use your fully functional device as a science experiment with water just because the device is water-resistant. Although it does carry an IP67 rating and is good for up to a meter of water for 30 minutes, any sort of water damage does void Apple's warranty on the device and many other companies have similar policies regarding water damage.