Waterboarding should be called controlled drowning. They actually fill the lungs with water, so your body is sending the signal "you're dying" to your brain. It's not about inducing pain: it's about inducing psychological trauma.
They're drowning you but "save" you just before you finally die (heart attack?)
That's why they put you on a flipping board: to quickly purge your lungs when they're loosing you (I doubt they do CPR).
Oh, and in the beginnings the Guantanamo bay inmates were choking with their own vomit: small chunks of food couldn't be flushed away from their lungs. Too many of them were dying, so no more chunky soup!
Du manger mou for you this week! Lucky you!
PS: If someone waterboarded me and after offered me the choice to rather have my throat slit (after reading a text before a camera), I'll probably choose the latter.