Damage is most certain around battery connector and majority under metal shields - data could be rescued in cca. 75% but 100% functionality of the phone almost never. Disconnect the battery ASAP and stop charging - your phone is already in Short circuit state so if you want to rescue any personal info from it - STOP USING IT and disconnect all cables
Check the connectors - for damage ( very often) - on both sides - cable and MB. A lot of times we can damage MB part because we try to force these connectors to sit in very delicate position. Reconnect them carefully (checking from the side to sit properly). Don't use any unnecessary force - if everything is O.K. you will feel and hear CLICK. Don't forget for a shield. Try with HARD reset as well (Home and Power button simultaneously for 10 sec. And if you didn't disconnect the battery before the procedure - well - there goes Micro soldering - Touch controller. Good luck P.S. and another common mistake: Screws are DIFFERENT lengths so be careful and use proper one at the proper place. Check twice with iFixit repair instructions which are which. In case that you used already longer screw on MB section you went through MB itself and only experienced Technician with advanced Micro soldering skills will be able to replace broken connections.
Definitely, try first with some other Power charger. If this is not the case then you have a problem with Power chip on your motherboard. You will have to find nearest Reair shop which is able to do a little bit of Micro soldering.
Even though battery maybe looks and behave OK we have to presume that it was under stress all this time under water so I strongly recommend new battery - it is not expensive and if nothing else - peace of mind is priceless
Well - this will be too much for yourself. Power circuit should be replaced on your motherboard - S6 & S6 Edge Power Supply PM IC Chip S2MPS15A0 for Motherboard. You will have to find some proper repair shop which is capable of doing micro repairs or contact: http://www.mendonipadrehab.com/ - Jessa is THE ONE!!! Check: Samsung Galaxy S6 Edge Teardown to see what is inside your phone