I personally, having experienced blocked breathing, don’t doubt I would give up immediately, although in fact I would not agree to what Hitchens agreed to. The additional component, breathing in of water, is entirely unfamiliar to me and I hope it stays that way.
A similar torture would be the old British one, part of their slow execution process, of hanging you until you are nearly passed out. All these guys who make excuses for waterboarding, they should have to agree it is alike to such hanging, or else suffer it until they do agree (which will take about three seconds), and if they do neither then they should be derided off the stage. (You didn’t think I was going to advocate non-voluntary waterboarding, did you? On the eve of Independence Day, no less? No, I’m just asking people nicely to do a service for their country, as Hitchens did.)