So you dropped your iPhone into the water. Unfortunately, it happens to the best of us. When I was working in an Apple Store, we would see people with the same problem every day, ranging from salt water to toilet water. It's never good, but it might not be too late to prevent water damage to your iPhone.
The very first thing to do is to gently remove your iPhone from the water and turn it off.
Now leave it off!
This is the most difficult thing I ask of you. Resist the temptation to check if your iPhone is still working and leave it turned off. The second you hit any of these buttons you might do more damage, so don't.
With that done, let's see what you need to do next.
What to do if you drop your iPhone in water
1. Turn it off immediately
2. Take your iPhone out of the case
3. Ease of liquid out of ports
4. Remove your SIM card
5. Wait for your iPhone to dry