you are experiencing the after effects of water damage. Unfortunately repairing your phone to get it up and running again would cost more than what the phone is worth.
If there is data stored on the phone that is irreplaceable then it may be worth it to you but the phone itself should be considered a write off.
If you drop your phone in water again here are some tips about what you should do
1. Do Take your battery out
2. Do NOT plug it into a charger
3. DO NOT attempt turn it on
4. Do NOT leave it to dry, put it in Rice/Silica gel or use a hair dryer on it. Water itself is not harmful to electronics, its the minerals in the water. So by leaving it out to dry you are only allowing the minerals to bake onto the board.
5. DO Wash it out in distilled water, give it a good 2-3 minute wash in distilled water to displace all the bad water before it deposits it's minerals on the board. Once it's deposited them, your options become very limited.
6. if you don't want to wash it out, take it to a repair shop who does micro soldering ASAP (While wet is best) and they will bring it back to life for you. They will possibly charge you less because you did the right thing too (I know we do)