Dunking is a form of corporal punishment used in the medieval and Early Modern (17th-18th century) period; however, it was more prominent in the middle of the 17th century.
Ordeal by water was associated with the witch hunts of the 16th and 17th centuries: an accused who sank was considered innocent, while floating indicated witchcraft. Some argued that witches floated because they had renounced baptism when entering the Devil's service. King James VI of Scotland (later also James I of England) claimed in his Daemonologie that water was so pure an element that it repelled the guilty.
The idea itself went back to classical times. Pliny the Elder in his Naturalis Historia, Bk. VII (ca AD 70), translator Philemon Holland, says: Hee <Philarchus> reporteth besides of these kind of men <sc. witches>, that they will never sink or drown in the water, be they charged never somuch with weightie & heavie apparel.
The ordeal would normally be conducted with a rope holding the subject connected to assistants sitting in a boat or the like, so that the person being tested could be pulled up if he/she did not float; the notion that the ordeal was flatly devised as a situation without any possibility of live acquittal, even if the outcome was 'innocent', is a modern elaboration.
Francois Maximilian Misson, a French traveller and writer, recorded the method used in England in the early 18th century:
The way of punishing scolding women is pleasant enough. They fasten an armchair to the end of two beams twelve or fifteen feet long, and parallel to each other, so that these two pieces of wood with their two ends embrace the chair, which hangs between them by a sort of axle, by which means it plays freely, and always remains in the natural horizontal position in which a chair should be, that a person may sit conveniently in it, whether you raise it or let it down. They set up a post on the bank of a pond or river, and over this post they lay, almost in equilibrio, the two pieces of wood, at one end of which the chair hangs just over the water. They place the woman in this chair and so plunge her into the water as often as the sentence directs, in order to cool her immoderate heat.
The dunking stool, rather than being fixed in position by the river or pond, could be mounted on wheels to allow the convicted woman to be paraded through the streets before punishment was carried out. Another method of dunking was to use the tumbrel, which consisted of a chair on two wheels with two long shafts fixed to the axles. This would be pushed into the dunking pond and the shafts would be released, tipping the chair up backwards and dunking the occupant.
In 2004, a soldier from the Singapore Guards died from a dunking incident during a Combat Survival Training course.
In its 2005 Country Reports on Human Rights Practices, the U.S. Department of State formally recognizes "submersion of the head in water" as torture in its examination of Tunisia's poor human rights record.