Even though many mobile phones today are quite tough and are designed to be "resistant" to water, it's never a good idea to expose them to water for too long. Still, this may be unavoidable, and if you have been unlucky to drop your phone into a sink of water, you may be in panic mode. Yet before you do anything that may cause additional damage, you may be able to salvage the phone by yourself if you take some specific actions. What do you need to do?
First Things First
If the phone was off when you dropped it into the water, do not be tempted to switch it on as soon as you retrieve it. If it was on when it took its untimely bath, switch it off right away once you get it out.
Remove the protective casing if you have one, and then eject the SIM card and battery if you can access them. Try to do this as gently as possible and without pressing any of the other buttons. Even though the phone is off, pressing some of the external buttons may drive the water further within, which you should avoid.
At this stage, you should try to remove as much of the moisture as you possibly can. If you have any silica gel packets, put the phone into a small container and add the packets on top. These will help to absorb the moisture if you leave everything in place overnight. However, if you don't have any of those leftover gel packets, place the phone in an area that is dry and warm. Try not to put it in direct sunlight, as this could cause damage, but leave it in this controlled environment for a couple of days if possible.
Some people may try to use a hairdryer, but this can be counterproductive unless they are very careful. Never place the appliance on maximum heat and try not to blast air into any of the openings. This technique may cause internal damage or push moisture further into the device.
Try to Reboot
After some time, you can try to reassemble the device and see if it will switch on. In an ideal world, this will do the trick, but sometimes the water infiltration may have caused more damage. In this case, you will need to call your nearest iPhone repair shop for advice. They will be able to assess the situation and help you to resume normal service.