iPhone XS is water proof to 2m, so why is it showing problems after <5secs at 10cm depth?

My wife’s iPhone XS went underwater for a couple of seconds, just below the surface for an ‘out of the water’ video shot. We thought this would be fine given it’s marketed as being good down to 2 metres.

it was fine at the time, but around 2 hours later it started to go through a repeating boot cycle. After a couple more hours (and drop in temperature) it booted up but Face ID didn’t work. It looks like there may be condensation in the camera but it’s hard to tell.

Where do we stand with this if Apple claim it’s ip68 rated to 2 meters for 30mins? Needless to say I’ve got one upset wife!