IP 67 and 68 ratings are rated for accidental water exposure, it is not waterproof and I am surprised so many YouTube reviewers fail to understand this. Neither Samsung or Apple provide warranties for water damage.
If you read the IP site you will see that IP67/68 is for still water, normal pressure, only for fresh water and IP68 does not mean IP65 tested so the S8 is not protected for spray like showers. Also it is very clear IP68 is not for use (pressing buttons) under water even fresh water.
It is literally for accidental drops in water. HTC have had to highlight this as YouTube and other reviewers seem to misinterpret the IP ratings. This whole OTT excitement at water resistance is all a bit weird and it has meant second hand values have fallen, as buyers are hesitant at buying water tortured phones.