The head is tilted back and water is poured into the upturned mouth or nose. Eventually the subject cannot exhale more air or cough out more water, the lungs are collapsed, and the sinuses and trachea are filled with water. The subject is drowned from the inside, filling with water from the head down. The chest and lungs are kept higher than the head so that coughing draws water up and into the lungs while avoiding total suffocation. "His sufferings must be that of a man who is drowning, but cannot drown."
Waterboarding is not:
- upright or face-down dunking: People dunked face-first in water can keep water out for as long as they can hold their breath. When one is inclined with the head back, holding one's breath will not prevent the upper respiratory tract from filling with water.
- asphyxiation: Survivors of near-drowning experiences report that the sensation of water flooding down the larynx and trachea as they struggle to breathe is the most terrifying aspect of the experience. In waterboarding, this begins quickly, long before the onset of oxygen starvation.
- submersion: Waterboarding does not require immersion in standing water. Someone can be waterboarded with as little as a canteen or two of water.
- slowly dripping water on the forehead: Several types of water-based tortures have been used in Asia, but the famous "Chinese Water Torture" demonstrated in Mythbusters Episode 25 is very different than waterboarding.
- a simulation: Waterboarding is actually forcing large quantities of water into the pharynx, and trachea, inducing choking and gagging in the subject.
Correction: Early drafts of this page indicated that waterboarding included inhaling water into the lungs. The recently declassified Bybee Memo's official procedure is to prevent this.