First-person experience

(H/t to tristero)

So, Christopher Hitchens decided that the only way to settle the question of waterboarding is to (you guessed it) be waterboarded.

He answers the "Is it...?" question in the title of his Vanity Fair article: Believe me, it's torture.

You may have read by now the official lie about this treatment, which is that it “simulates” the feeling of drowning. This is not the case. You feel that you are drowning because you are drowning—or, rather, being drowned, albeit slowly and under controlled conditions and at the mercy (or otherwise) of those who are applying the pressure. The “board” is the instrument, not the method. You are not being boarded. You are being watered.

Admittedly, Hitchens credentials as an objective observer are less than ironclad. It's not clear Hitchens motivations are deeper than merely wanting to annoy those he finds annoying.

However, I think his account of the experience (once you boil off the ego) does add to the conversation.
That he has been a booster of US Iraq policy in the past is merely seasoning.

He is a pompus ass, to be sure - but he can write a good aphorism:

I apply the Abraham Lincoln test for moral casuistry: “If slavery is not wrong, nothing is wrong.” Well, then, if waterboarding does not constitute torture, then there is no such thing as torture.

 Well put.