Mamapa2the major issue you will run into is corrosion damage. Salt Water will get your components to corrode very severely. You do no longer want to try to turn your phone on, charge it or mess with it until you have done teh following.
The very first thing I would do is to disassemble it by using something like [https://www.youtube.com/watch?v=9hNLSvcF23A|this video] Take a careful and close look at all components and connectors. Truly assess the damage. Look for major corrosion, evaluate the pins in the connectors etc,. Take a look at all connectors as well as cable ends. After that I would suggest that you clean it a couple of times in '''sterile''' water, not drinking water (that might have helped right after it got submerged in the salt water). Use a soft brush and clean it very, very thoroughly with the sterile water. For a proper cleaning , you must remove all the EMI shields. Once you got the gross contamination cleaned, use 90%+ isopropyl alcohol and clean your parts some more (50% is just not enough since the other 50% is mostly water). For a proper cleaning, use [guide|5825|this guide.] It was written for a iPhone 3G but it is still pertinent to your phone as well. I can not stress the importance of a good cleaning enough, so do it over and over while replacing the alcohol after each cleaning. Do not use compressed air for the cleaning since that can drive liquid as well as corrosion particles into areas that will cause trouble later on. Do not use drinking water, if you need to use water, use sterile water. Also, you do not need to leave it to dry for a day. Isopropyl alcohol in the higher concentration will evaporate quickly and dissipate the water. The importance here is '''the cleaning'''. It would of course be best to get it professionally cleaned with an ultrasonic cleaner. Do not forget to '''replace the battery'''. This is a '''must''' and not an option. After that, reassemble your phone and see what you get.
For as long as you have not cleaned your board and replaced the battery, everything is just a guess. Keep in mind that water damage is the hardest to troubleshoot and to repair. It does not matter if is was exposed for 2 seconds or 2 hours, what matters is where the water (particulates) did the damage. If you see something odd or find something that does not look right, you can always post pictures with your question for further help. [guide|21499]
Remember: Rice does not work!!!!!!