The Ducking Stool
The prisoner would be strapped into a seat which hung from the end of a free-moving arm. The seat and the suspect would be dunked into the local river or pond. It was up to the operators of the stool as to how long she remained under the water. Many elderly prisoners were killed by the shock of the cold water --others just drowned.
The Ducking stool was a punishment strictly for women. It was used as punishment for prostitution and witchcraft.
Ducking was seen as a foolproof way to establish whether a suspect was a witch. If the 'witch' floated it was deemed that she was in league with the devil. If the 'witch' drowned she was deemed innocent.