My Face ID have a problem
My phone fall inside the water so the Face ID is not working again
Liquid damage may have compromised the functionality of your iPhone but we, just users like you, cannot diagnose that issue remotely, sorry.
I suggest that you make an appointment (*) and have your device inspected at an Apple Store or AASP (Apple Authorized Service Provider) among this list:--> https://locate.apple.com/choose-country-region . After checking it out, they'll give you all the available options.
Regards
Giulio
(*) You can do it:
- Online:--> Genius Bar Reservation and Apple Support Options - Apple;
- Contacting a local Apple Store or AASP among the list provided above;
- Using the "Apple Store" app, available and downloadable from AppStore.