The prisoner also knows that if he LIES and the information os a pack of LIES, you're going to be BACK, for further discussions. And it might not be as gentile. Waterboarding is 90% imagination (I'm gonna DIE! SO, i'LL GIVE IT ALL UP!) AND 10% discomfort. As I said, as a surfer and SCUBA diver I have been in bad places due to nature and my own stupidity. More than once battered by pre-hurricaner surf, held under water by rolling surf for over a minute, no safe word, , just brown black and being tumbled over rocks, quick half breath, and another roller in the face and down again.
Once, while SCUBA DIVING Imade an ascent from 165 ft to 50 ft (decompression station) withouit a inhaled breath, same speed as my bubbles, exhaleing all the way to the safety tank and regulator.
YOU CAN DO IT. But panic would get a desert dweller, I think, and he give everything up.