Remember the keynote presentation? When Apple showed this when representing iPhone 7, people started to think it’s water proof phone. I do not know why and how, but I have to tell my customers that it’s water resistant, not proof!
http://www.trustedreviews.com/opinion/what-is-ip68-ip-ratings-explained-2947135 is a very good article explaining IP67 and IP68.
Anyway, the reason why I am posting about this to let you know that no matter what you do, moisture will affect the phone.
The picture below is from iPhone 6s which had water resistant seal and the phone was in protective case and was never been exposed to the water. However this phone was brought in for charing issue and as you can see, there are corrosion on the connectors. That is inside and under. Apple does cover up the connectors with underfill to prevent moisture and dust but that will not protect your phone forever.
