Hi @loximity ,
How do you propose that the distilled water is going to displace the sea water etc.?
Some of the sea water may get "stuck" inside the phone as you are not washing it away with distilled water by just submerging it in it, simply trying to dilute it somehow. Also allowing it to dry without all the sea water having been removed still allows for corrosion to occur.
Only sure method is to open it up and dis assemble it. You can then use distilled water to flush away the sea water.
Also whilst the battery is still connected there is still the potential for electrical damage due to the salt water conducting electricity (not the distilled water - it doesn't conduct)