During the time in which "dunking" was considered a test/penalty for witchcraft, why was is exceptional for someone not to sink in water? People in this time grew up around lakes and rivers and seas, why couldn't they swim?
Follow-up question: Was it exceptional for witches to float, or was saying "if it floats, it's a witch" mainly a way for them to declare as many people witches as possible (since a person full of air will often float)?