ashish, for proper trouble shooting you can always try and clean it first. The very first thing you want to do is to not try to restart the phone. This may further damage your phone. you also do not want to try to charge it any further. The next thing to do is to clean it. Disassemble your phone using these guides Once it is disassembled, you do need to clean it properly. You will need high grade isopropyl alcohol and a soft brush. Use this guide to see how to clean it. Even so it was written for a 3G all the points are still pertinent to your phone. Do not forget to remove the EMI shields for proper cleaning. While you are cleaning it, check for any broken, missing or burned looking components. When it is properly cleaned, replace the battery. All these steps are to avoid delayed failure caused by corrosion. Once all this is done, reassemble your phone and reevaluate. Water damage is the most difficult to diagnose since virtually any part may have failed. If you replace the logicboard, you will not have access to any of your files that are saved to your current phone etc.