Could you submerge any electronic device (with no applied power) and see no ill effects?
Yes in fact some assembly processes wash boards coming off the assembly line.  Can you wash everything?   No.  Someone may correct me but if I remember right electrolytic caps for example can absorb water.   Things like switches may trap water or oxidize and corrode contacts when that standing water gets left on there.   Pretty sure electret mics don't like it nor would speakers and qfns often trap water for days.

But I'd say in general fully discharged and unpowered, then fully dried and perhaps baked it should work again.

Look at this thing it's basically an overgrown board dishwasher :)