Mate whatever you do not turn your phone on for few days even with a new or differrent battery! Let it completely dry out! Use special alcohol containg liquid for cleaning getting rid of sea water and salt crystals its better then distilled water as it quickly evaporates after its done its job so it will quicker drying process! Put your phone completely submerged in a air tight container full of rice with the keyboard open obviously without the back cover on and facing upwards helps also put battery in there as well for a day or two! If you have central heating in your house then put it on top of your radiator facing upwards for a few hours with moderate warm temperature dont put heat temperature too high! Only after you are 101 percent sure then put battery in and give it a go and see if it starts up if it does you are lucky but if you see any sign of water on screen then imediately remove battery repeat drying process leave it for another day or two and check again! the longer you dry it safer it is and more chances of you not destroying the phone even if it was recoverable by voltage spike!
Oh and good luck!