In 1987 a Star Trek book anticipated the use "enhanced interrogation" (in those terms) by simulated drowning.

And this was in the context of a despotic leader plotting to undermine civil rights by creating or inflating the threat from an enemy. It even anticipated the battle over where or not the practice was properly called "torture."

[By the way, I know that waterboarding predated the US use of it. Specifically, it was a technique believed to be used by the Chinese, which is how the US started working with it as they tried to train American troops not to be vulnerable to it. But:

(1) its use wasn't widely known mongst Americans before its use in the Iraq war, and, more to the point,

(2) its use in this story by a planet that is a member of the Federation of Planets, rather than the Klingons or Romulans or other obvious baddies, means that in this story is equivalent to its use by the US.]

The book was "Deep Domain" by Howard Weinstein (http://www.amazon.ca/Star-Trek-33-Deep-Domain/dp/0671633295/ref=sr_1_2?ie=UTF8&s=books&qid=1278727292&sr=8-2). Here's a short quote:

The hallway was barely wide enough for two to walk shoulder to shoulder, with stone-block walls that angled in as they reached the ceiling. There was little doubt the Citadel was quite old, but plenty of bright lighting made this section seem somewhat less dungeon-like. Vvex led the way down a short flight of steps to a vaulted room with museum piece torture racks and shackles around the perimeter. But the dominant features were a pair of clear, modern tanks, three meters high by two across and filled with water. Each one had a winch over the open top, and Chekov's jaw dropped in horror when he realized that one of the tanks was occupied by a naked man, hanging upside down from the winch, flailing and writhing, trying vainly to right himself and rise to the top. Every time he seemed about to succeed, the guard operating the winch would yank the prisoner up, dangle him by his feet in the air for a second, then dunk him back into the water.

The corners of Spock's mouth tightened, and Chekov noticed. It was as close as he'd ever seen the Vulcan come to betraying anger. "I had been led to believe that Akkallans were too civilised to resort to torture, brigadier."

"Oh, this isn't torture, commander. It's just an interrogation enhancement technique, useful for softening resistance."

'`That's what he said," Chekov sneered. "Torture."