The threat of imminent death is not only experienced on the waterboard (there are known, serious medical events on the board), but also in SERE there are mock executions.
When another is being question while the primary is on the board, in the fitful throes of what seems like imminent death, that applies to #4.
Even ebing witness to such and event will burn in your memory forever. For those who participated, PTSD candidates all.
Nobody has ever applied the waterboard who has not been on it themselves. That's rule #1.
this is where we differ, a gun to the head/knife to the throat is a threat of imminent death and medical events on the board are collateral to the process not the intended outcome, that is why when KSM and his cohorts were on the board there were medical personnel in attendance
honest question: how long did you last on the board