Unfortunately mac is not brothproof. You are lucky one if it still works after contact with water. Usually devices and water do not mix and water damage is not covered by warranty. I assume corrosion has already started. You should schedule a genius appointment at the Apple Store to appraise the level of damages. They will offer you the best solution.
Anyway you may try these steps:
Try Safe Boot:
- Shut down your Mac
- Wait until your computer turns off and after that press the Power button
- Right after you hear the startup tone, press and hold the Shift key
- Release the Shift key when you see a grey Apple sign and the progress bar below this sign
- After your Mac boots up, restart it as you usually do.
If this doesn't help, follow the instructions below:
- Shut down your Mac
- Wait until your computer turns off and after that press the Power button
- Right after you hear the startup tone, press and hold the Shift key
- Release the Shift key when you see a grey Apple sign and the progress bar below this sign
- Once you see Desktop, start a Disk Utility scan to detect and repair file system errors (don't forget to choose your main hard drive)
- Click on Verify Disk and then, if asked to fix problems, on Repair Disk
- After this, click on Verify Disk Permissions and then on Repair Disk Permissions
- After the process is finished, shut down your Mac and turn it back on after about 30 seconds
Apart from that, take a look at this Apple article and follow the instructions on Resetting NVRAM shown there: How to Reset NVRAM on your Mac - Apple Support
Try resetting the System Management Controller: https://support.apple.com/en-us/HT201295
Take a look at the steps suggested by Apple in this article:
https://support.apple.com/en-us/HT204267
Good luck.