There are probably mint stamps that have gone through a washing / soaking / floating but when this happens they usually (as most stamps do) lose there glossy reflective shine on their fronts.
People still wash stamps off and reuse them when they have been postally used but it is against the law. Just don't get caught.
I collect used stamps and enjoy a good readable cancel or postmark, as do many. Others collect mint, post office fresh stamps, with the gum still on, intact and pretty as a picture.
Looking on
ebay or Bidstart or Delcampe web sites will show many stamps sold as postally used and cancelled as well as many mint ones too of course.