Hi there, all,
Years ago I read in a SCUBA diving magazine that in the event of an underwater camera case leaking, the rescue procedure was to first flush with fresh water (if the leak was in sea water) to get rid of the salt. Then follow that up with a generous rinse with methylated spirit (UK terminology, = denatured alcohol in the USA?). Any remaining water combines with the alcohol to form an 'alletrope'. Tip away the bulk of the alcohol and ventilate the item. When the residual alcohol evaporates, it takes any remaining water with it.
I eventually had an opportunity to try the procedure when one of our diving club members went into the sea wearing a family heirloom wristwatch! I'm happy to report that, in that case at least, it was completely successful. The only proviso is that, in the case of a wristwatch, the successive irrigations, first with water and then with the alcohol, completely remove the lubricant from the watch movement and potentially introduces dirt. So the immediate rescue treatment MUST be followed up with a clean and lubrication by a competent watchmaker.
In the case described above, it was easy to remove the watch movement from its case. In another event, a colleague's diving watch sprang a leak and we couldn't open the case to gain access to the works. By the time the owner of that watch got it to a watchmaker, the sea water had completely corroded through the spokes of some of the wheels! Time is of the essence!!
If the casualty includes electronics circuitry, then yes, remove the battery ASAP.