It's no secret that Donald Trump is a fan of waterboarding. He's said multiple times , as recently as this week's debate, that he doesn't think it should be considered a war crime, and that if elected he'd work to make it acceptable under international law.

Torture was banned during the Geneva Conventions, and waterboarding is widely considered torture by everyone from the U.S. Justice Department to Amnesty International , legal experts and the United Nations . The United States, under President George W. Bush and thanks in part to the efforts of Deputy Assistant U.S. Attorney General John Yoo, waterboarded people . Yoo still defends our use of the practice, but says that Trump is totally misunderstanding it.

"I'm afraid Mr. Trump thinks of waterboarding, or worse, as a kind of punishment, like a sentence -- as you said, revenge or reprisals," he told Fox News' Brian Kilmeade on Tuesday. "That's not what its purpose is. The purpose of it is not to take revenge for past acts. It's to figure out what to do now to get intelligence to stop future attacks."

Research has shown that "enhanced interrogation tactics" like waterboarding don't actually work . But that doesn't seem to faze Trump, who's said that even if torture isn't successful in extracting information from suspects, "they deserve it anyway."

"Would I approve waterboarding?" he said during a November campaign rally. "You bet your ass I would. In a heartbeat. I would approve more than that. It works and if it doesnt work, they deserve it anyway for what they do to us."

Editor's note: Donald Trump is a serial liar , rampant xenophobe , racist , misogynist , birther and bully who has repeatedly pledged to ban all Muslims -- 1.6 billion members of an entire religion -- from entering the U.S.