All iPhone 12 models have a built-in liquid contact indicator (LCI) that changes from white to red if it comes in contact with liquids. You can find this sticker by opening the SIM card tray under the power button on the side of the iPhone 12. An LCI will activate when it comes in contact with water or a liquid containing water. The color of the indicator is usually white or silver, but when it comes into contact with water or a liquid containing water, it turns completely red. An LCI does not activate due to changes in humidity and temperature that are within the environmental requirements of the product.
You may think that charging your phone is a good idea, but this can cause further damage, since electricity and water are a dangerous combination. The water damage indicator is normally located inside the iPhone, in the SIM card slot for iPhone models, such as iPhone 5, CE, iPhone 7, 7 plus, and iPhone X and up. When you take your device to the Genius Bar for repair, they can determine if it has been damaged by water. If a liquid damages an iPhone or iPod (for example, coffee or soda), service for damage caused by the liquid is not covered by Apple's One-Year Limited Warranty, but you may have rights under consumer law.
We recommend that you take maximum care of your device to avoid exposure to water or any fluid that may cause liquid damage. The water damage indicator or liquid sensors are positioned to indicate that liquid has entered the iPhone. That's a significant indicator of the humidity inside the device, a strong indication that it could have water and be damaged. Again, Apple's iPhone warranty doesn't cover water damage, even when it involves water resistance.
That means that the liquid contact indicator (LCI) on the phone has been activated and that water or other liquid (looking at you, coffee) entered the phone and is likely to damage it. There are several indicators of water damage on the iPhone that you should be aware of, including turning the device on and off, the silence of the phone, and a failure in the apps. However, liquid indicators may activate due to other factors that are not authentic and are not caused by water damage problems. If your iPhone accidentally comes into contact with water (or other liquid) for a short period of time so that it only exposes the speakers, there are a couple of ways to fix this situation by drawing water from the iPhone speakers.
But the guys at Apple can open the phone to see moisture or liquid debris or corrosion, which definitely indicates water damage.