Iphone 6 under warrenty. I had the phone in a backpack with friend Samsung galaxy6 along with couple water bottles. Iphone went dead so took it to Apple Store and explained possible water damage. They said no warrenty coverage and told me $300 to open and fix. Tried to explain phone never went underwater but no use. I told my friend with Samsung Galaxy6 and he said his phone is fine and sent me Utube link to underwater test. Next phone is Samsung.
I Wouldn't dunk a Samsung. I love my Samsung phones, Ive owned several, but those water tests on the phones, active or not, make me wince. In fact the current GS7 active has failed the dunk test, whole the regular s7 and s7 edge passed.
I Prefer a ziploc freezer bag.
There is a difference between "water damage" and "underwater." A phone can be easily damaged just by spilling on it in the wrong place. For example, if you set a drippy bottle on the uncracked screen of your phone, you're probably fine. But if your phone sits in/on a puddle on end, regardless of how long, you will most likely have the water marker tripped, if not actual damage to the charging or auxiliary port.
I Bet the YouTube video was someone else's phone and not your friend purposely putting his phone in water.
Even if you had this phone, it is water resistant not water proof. Any water damage would still not be covered under warranty.