@jeonjk5617 First thing to do is to STOP continuing to try to charge, sync or otherwise use your phone. This potentially can make a bad situation worse. This may further damage your phone.
The next thing to do is to clean it. Disassemble your phone using rhese guides Samsung Galaxy S21 Ultra Repair Remove all the circuit boards.You must remove all EMI shields of those boards. If you do not remove those, you might as well not do anything. After you removed those, clean the whole boards, connectors and all with +90% isopropyl alcohol (if you can get 96 or even 99%). Follow this guide, and even so it was written for an Apple iPhone 3G, all the points are still pertinent to your phone. While you clean your boards, check for any obvious damage, like burned or missing components etc. When everything is properly cleaned, replace the battery. All these steps are to avoid delayed failure caused by corrosion. Best thing to do, would be to clean it with an ultrasonic cleaner, but if you do not have access to one, this will at least help. Once all this is done, reassemble your phone and reevaluate. Until it is cleaned, everything will only be a guess. Even with all this, water damage has only a small chance to be fully repaired, but at least you can give it a try.