The way I saved my GF's iPhone, after running through a full cycle of wash, was by:

--disassemble immediately
--soak in rubbing alcohol for a few seconds (so that alcohol repels water moisture and drying become quicker; as well as to wash away any water impurities that may show up after drying)
--blow dry with compressed air (make sure the streaming air if not to close or part of phone can get blown off and/or moisture could get forced into more places)
--then leave for a full day in a sunny hot car in a bowl of rice

All of that was immediately done after discovering the iPhone being soaked in water. Odds are, if you left it soaked overnight, that there's enough corrosion the next day for the device to be irreversibly damaged. This is especially true with salt/ocean water. My previous phone, BlackBerry, didn't even survive a couple of hours after being immersed into ocean water, as the metal contacts have crystallized by the time I got home.