Welcome to Android Central! See this guide:
http://forums.androidcentral.com/amb...e-got-wet.html. The problem here is that we're talking about sea water, which is terrible for the phone's inner workings. Water damage can be unpredictable and insidious--so even though most of it is working ok now, more problems may crop up weeks or months from now as corrosion develops and spreads.
You could try the methods of drying the phone mentioned in that link, and also backup whatever data you can right now, before it's too late. If the phone starts working better, then keep using it--but always keep your data backed up or synced regularly, since the phone will have a much higher chance of sudden failure. Unfortunately, warranty repair is out of the question, since there are probably water exposure sensors inside the phone that will let technicians know if any moisture got in.