It is the practice ("art" according to Dick Cheney, who has mastered it) of strapping a person to a slab with their head pointed toward the ground, wrapping cellophane around their head and dumping water on them. It simulates drowning, but usually without death, only horrible psychological problems and several broken bones. Those lovely gentlemen in the Spanish Inquisition referred to it rather less euphemistically as "the drowning torture".
It is practiced in the US military base Guantanamo Bay in Cuba, which somehow negates the fact that it's torture because it's technically in Cuba. So basically, America never went into Iraq in the first place. It is only a war if someone takes buckets of good American dirt and throws them at their enemies. Otherwise, it's just not America attacking.
The U.S. State Department has recognized that other techniques that involve submersion of the head of the subject during interrogation would qualify as torture. In its 2005 Country Reports on Human Rights Practices, the U.S. Department of State formally recognizes "submersion of the head in water" as torture in its examination of Tunisia's poor human rights record, U.S. Department of State, 2005, Tunisia  and current US Attorney General, Eric Holder is holding an investigation. 
The United Nations Report of the Committee Against Torture: Thirty-fifth Session of November 2006, stated that state parties should rescind any interrogation techniques, such as waterboarding, that constitutes torture or cruel, inhuman, or degrading treatment or punishment.
"The person believes they 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. 
- ↑ *U.S. Department of State.
- ↑ http://www.state.gov/g/drl/rls/hrrpt/2005/61700.htm Country Reports on Human Rights Practices]
- ↑ Report of the Committee Against Torture: Thirty-fifth Session (14 - 25 November 2005); Thirty-sixth Session (1-19 May 2006), United Nations Publications, p.71, isbn=92-1-810280-X