There are several different varieties of interrogation techniques referred to as waterboarding.
n the medieval form of waterboarding, a victim was strapped to a board and tipped back or lowered into a body of water until he or she believed that drowning was imminent. The subject was then removed from the water and revived. If necessary the process was repeated.
There are other forms, but all of them have in common that the victim almost drowns but is rescued or re-animated just before death occurs. The technique is designed to be both psychological and physical. The psychological effect is that the victim is led to believe that he or she is being executed. This reinforces the interrogator’s control and makes the victim experience mortal fear. The physical effects are extreme pain and damage to the lungs, brain damage caused by oxygen deprivation and sometimes broken bones because of the restraints on the struggling victim.
A similar technique was applied to punish scolds and detect supposed witches. In a trial by ordeal called “dunking” or “ducking,” supposed witches were immersed into a vat of water or pond, and taken out after some time, when the victim was given the opportunity to confess. If she confessed, she was killed; if she did not confess, she was submerged again. This process was usually repeated until the victim either drowned or submitted herself to execution in another way (hanging or, rarely, burning).
Current uses of waterboarding
The current practice of waterboarding was known previously as “the water cure.” It involves tying the victim to a board with the head lower than the feet so that he or she is unable to move. A piece of cloth is held tightly over the face, and water is poured onto the cloth. Breathing is extremely difficult and the victim will be in fear of imminent death by asphyxiation. However, it is relatively difficult to aspirate a large amount of water since the lungs are higher than the mouth, and the victim is unlikely [but quite possible] actually to die if this is done by skilled practitioners. [No definition of skilled practitioners provided by Wikipedia, but when used with the word torture, it should probably be found in close proximity to executioner or bully. Required qualities for such a practitioner would be a rather low self esteem and a desire to see others suffer. These qualities are regularly found in armed services and guards. Furthermore, people doubt this are generally those same people who would perform torture on others. It is nothing more than a sadistic practice that has no positive outcome on gaining truthful information. Quite the contrary, even the military has stated repeatedly that tortured prisoners state what their torturers want to hear in order to stop the torture. This fact is obvious once someone experiences waterboarding. Experiencing waterboarding is to experience drowning.] Waterboarding may be used by captors who wish to impose anguish without leaving marks on their victims as evidence.
This is a technique demonstrated on U.S. military personnel by other U.S. military personnel when they are being taught to resist enemy interrogations in the event of capture (see SERE below).
On Nov. 18, 2005, Brian Ross and Richard Esposito described the CIA’s “waterboarding” technique as follows in an article posted on the ABC News web site: “The prisoner is bound to an inclined board, feet raised and head slightly below the feet. Cellophane is wrapped over the prisoner’s face and water is poured over him. Unavoidably, the gag reflex kicks in and a terrifying fear of drowning leads to almost instant pleas to bring the treatment to a halt. According to the sources, CIA officers who subjected themselves to the water boarding technique lasted an average of 14 seconds before caving in. They said al Qaeda’s toughest prisoner, Khalid Sheik Mohammed, won the admiration of interrogators when he was able to last between two and two-and-a-half minutes before begging to confess. ‘The person believes they [sic] are being killed, and as such, it really amounts to a mock execution, which is illegal under international law,’ said John Sifton of Human Rights Watch.” 
Dr. Allen Keller, the director of the Bellevue/N.Y.U. Program for Survivors of Torture, has treated “a number of people” who had been subjected to forms of near-asphyxiation, including “water-boarding,” in which a suspect is bound and immersed in water until he nearly drowns. An interview for the New Yorker states:
He argued that it was indeed torture. Some victims were still traumatized years later, he said. One patient couldn’t take showers, and panicked when it rained. “The fear of being killed is a terrifying experience,” he said. 
(1) CIA’s Harsh Interrogation Techniques Described Sources Say Agency’s Tactics Lead to Questionable Confessions, Sometimes to Death
BRIAN ROSS and RICHARD ESPOSITO / ABC News 18nov2005
(2) Outsourcing Torture: The Secret History of America’s “Extraordinary Rendition” Program JANE MAYER / The New Yorker 14feb2005
In an editorial Thursday (free registration required), the Wall Street Journal describes waterboarding as “the most coercive interrogation technique that was ever actually authorized” against Al Qaeda. According to the Journal, “it involves strapping a detainee down, wrapping his face in a wet towel and dripping water on it to produce the sensation of drowning.” This, the Journal says, “is pushing the boundary of tolerable behavior” but the editors ask for a debate on the question of whether it is “immoral, or unjustified, in the cause of preventing another mass casualty attack on U.S. soil.”
This afternoon, James Taranto quotes the Journal’s definition in his Best of the Web Today column on the WSJ’s OpinionJournal.com site, using it to mock Ted Kennedy, who referred to descriptions of waterboarding as “drowning someone to that kind of point” during confirmation hearings for Alberto Gonzales yesterday.
But dripping water on a towel didn’t sound like what I had read about in the past, and it turns out that other journalists describe the practice very differently than the Journal. The New York Times reported in May that waterboarding was used by the CIA on Khalid Shaik Mohammed, an Al Qaeda leader. This is how the paper described the practice: “a prisoner is strapped down, forcibly pushed under water and made to believe he might drown.” No towels, no dripping — the prisoner is pushed under water. And today the Washington Post defined waterboarding as “an interrogation technique in which a detainee is strapped to a board and pushed underwater to make him think he might drown.”
So who’s right? This is a hugely important issue, both for US policy toward its prisoners and for the Gonzales confirmation hearings. It would be nice to get some clarity from the press.
Update 1/19: Taranto points out by email that a January 4 story in the Post uses the Journal’s definition. I’m emailing the paper to try to get some clarity on this. I’ll update this post if I find out more.
Update 1/20: R. Jeffrey Smith, one of the authors of the January 4 story cited above, responded to my email to say that he is confident that the dripping-water definition is correct:
Mr. Nyhan —
Thank you for calling attention to conflicting accounts in the Post and other newspapers of the interrogation technique known as waterboarding. I am utterly confident — based on careful reporting — that the description of this technique in our recent article about Mr. Gonzales is a correct and complete account, and that the other depictions are, at best, loosely paraphrased accounts of this technique.
All best regards,
R. Jeffrey Smith
source: http://www.brendan-nyhan.com/blog/2005/01/what_is_waterbo.html 24dec2005
What is Waterboarding? (Part II) BRENDAN HYHAN / Blog 13feb2005
About a month ago, I pointed out that the Washington Post and other publications have published contradicting definitions of the interrogation tactic known as “waterboarding,” which is either strapping someone to a board and submerging them under water until they think they are about to drown, or placing a wet towel over their face and dripping water into their nose until they think they are about to drown. While both tactics are brutal, the first seems especially horrific, at least to me.
So what is the right answer? When I contacted Post reporter R. Jeffrey Smith, he claimed that he was sure that the towel definition was correct based on his reporting. But New Yorker writer Jane Mayer uses the submerging definition in an article in the latest issue of the magazine:
According to the [New York] Times, a secret memo issued by Administration lawyers authorized the C.I.A. to use novel interrogation methods—including “water-boarding,” in which a suspect is bound and immersed in water until he nearly drowns. Dr. Allen Keller, the director of the Bellevue/N.Y.U. Program for Survivors of Torture, told me that he had treated a number of people who had been subjected to such forms of near-asphyxiation, and he argued that it was indeed torture. Some victims were still traumatized years later, he said. One patient couldn’t take showers, and panicked when it rained. “The fear of being killed is a terrifying experience,” he said.
The New Yorker is a carefully fact-checked magazine. It’s possible Mayer is depending on the Times reporting, which uses the submersion definition, but it’s hard to believe that wouldn’t have been independently verified. Once again, what’s the right definition? The mainstream media is continuing to fail to precisely define a key term in the debate over US interrogation practices.
[source: http://www.brendan-nyhan.com/blog/2005/02/what_is_waterbo.html 24dec2005]