For the sake of your phone please STOP trying to turn it on!
At a minimum, you will need to get a new battery. The battery is the 1st thing to get ruined or short out when wet. When that is replaced, it will most likely turn on, but you are not out of the woods...
Your iPhone's days will be numbered but a few, depending on the extra steps you take.
Just because it turns on now doesn't mean it won't crap out a few weeks down the road...
Resist the urge to turn it on for now. You (or someone qualified) should remove the back cover (2 bottom special screws) and disconnect the battery to prevent damaging corrosion on your circuit board.
You need remove battery power and your circuit board needs to be cleaned in an IPA (alcohol) bath. If you're willing to take an extra step to protect your iPhone, you should get a professional "Ultrasonic Cleaning" and a new battery. If corrosion found on the logic board is minimum, many potential problems are eliminated.
Sometimes, peripherals such as cameras can also start overheating or cause battery problems after liquid exposure, too. They can be disconnected or replaced.