Professor of theological ethics and director of the Martin Marty Center at U. Chicago’s divinity school, William Schweiker provides more historical background on the practice of waterboarding:
In the Inquisition, the practice was not drowning as such, but the threat of drowning, and the symbolic threat of baptism. The tortura del agua or toca entailed forcing the victim to ingest water poured into a cloth stuffed into the mouth in order to give the impression of drowning. Because of the wide symbolic meaning of “water” in the Christian and Jewish traditions (creation, the great flood, the parting of the Red Sea in the Exodus and drowning of the Egyptians (!), Christ’s walking on the water, and, centrally for Christians, baptism as a symbolic death that gives life), the practice takes on profound religious significance. Torture has many forms, but torture by water as it arose in the Roman Catholic and Protestant reformations seemingly drew some of its power and inspiration from theological convictions about repentance and salvation.
Schweiker’s column is worth reading in full, as he explores the unverbalized but plausible religious implications of the use of waterboarding by the U.S. government.