Try detaching yourself from waterboarding. From gagging. From drowning. From physical pain. I was at the dentist for a filling repair and the apparatus they were putting in my mouth for water rinsing and cooling and water removal made me feel like I was going to choke to death and I immediately spit it out and they used a different device. Even so I was concentrated on trying to remain calm and breathe like when I snorkel. I got through it with effort and had to joke about it with myself "embrace the suck" when life sucks, no pun intended.