I suspect that the seals may not have been replaced/renewed properly and no pressure testing was carried out to check that it was still water resistant. Note, the phone is not waterproof, only water resistant! Probably not a good idea to attempt underwater photography with it.
“iPhone 11 Pro and iPhone 11 Pro Max are splash, water, and dust resistant and were tested under controlled laboratory conditions with a rating of IP68 under IEC standard 60529 (maximum depth of 4 meters up to 30 minutes). Splash, water, and dust resistance are not permanent conditions and resistance might decrease as a result of normal wear. Do not attempt to charge a wet iPhone; refer to the user guide for cleaning and drying instructions. Liquid damage not covered under warranty.”