iPhone XR fell in water and Face ID won’t work

Hey there,

See ☞ If Face ID isn't working on your iPhone or iPad Pro - Apple Support

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See ☞ If an alert says Face ID has been disabled on your iPhone or iPad Pro - Apple Support

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See ☞ Water and other liquid damage to iPhone or iPod isn't covered by warranty - Apple Support

y_p_w is correct. The phone will need to be replaced. Apple won't try to service a water damaged device. They'll offer you an Out of Warranty replacement, per the prices in this link --> iPhone Repair - Official Apple Support

Personally, I would not spend $399 for an Out of Warranty Replacement on an iPhone XR. I'd use that money and put it towards a newer model iPhone. Your choice of course.

There's really not much you can do as it's typically a hardware malfunction, and one that won't get better without repair or replacement. Replacing it would probably be the only thing that would take care of the issue.