@thomasfuchs just an anecdote, no idea if this is a common experience.
i dropped my iPhone X in my hot tub from water hight. it was about 3 weeks old, basically new, and had never been dropped or mistreated before.
it fluttered to the seat ~0.5m underwater. temperature set to 38°. it definitely didn’t hit hard, on a corner, or scratch the case-less glass at all.
i picked it up immediately and it seemed fine. time/depth all well within water specs.
totally bricked 2 hours later.