There's YouTube videos of previous iPhones hanging out underwater for an hour with no problems. I think this is more of an official rating or whatnot.

Worth noting that this isn't new to iPhones, and it was introduced last year specifically in regards to protecting against falling into a pool.

The first footnote claims an IP67 rating

I bet they still don't cover water damage.

That's what I'm afraid of. I have the 6s Plus right now and when going swimming with kids and recording stuff, I'm always terrified of dropping the phone into the water. Yet, the apple watch can be submerged fine.

6S wasn't rated as water resistant, only 7 was.

Yes