More than likely it is time to get a new phone. If your phone is ever submerged in a liquid power off and get the battery out A.S.A.P. Use the breakdown guides on ifixit to open it up where you can get to the most crucial components. I use a small watercolor paint brush to thoroughly "paint" logic board and any other areas that received water damage with 90% isopropyl alcohol. At time Ive even placed the board in a container big enough to submerge the component. The alcohol will merge with any water you are not able to remove and evaporate. Let it dry but don't use it until you are certain you've removed all water. Your phone sound like it had corrosion to the crucial parts and/or corrosion built up until it shorted the battery of and number of pathways that is inhibiting electricity to flow along its designed path. It can't hurt now to disassembly and look for greenish corrosion and even brush those areas with alcohol. You could also try soaking the board in the alcohol to loosen the damage, like rust, and see. Anything is possible.