I never understood the advice to submerge face into icy water when under AF episode. This morning, my friend (nurse) mentioned this if I felt rapid heart rate and AF attack. His explanation was something called "Mammalian Diving Reflex".
I checked Wikipedia and voila:
"Bradycardia is the first response to submersion. Immediately upon facial contact with cold water, the human heart rate slows down ten to twenty-five percent."
I just wanted to share this with you in case some you didn't know this interesting cause and effect.