It simulates drowning without the threat of actually dying, but you’re convinced that you *are* drowning, thus the terror factor is high.
And if you do die. You can be revived, it's not like they leave you dead for 15 minutes, eeeehhhh I'd say 30 seconds of death doesn't do too much brain damage, I would even go out on a limb to say it does very little. It's not like your getting your finger nails ripped off or your eyelids removed........It's a "Dunk In The Water" lets be a little more tolerant of our Operatives doing what's best for all.