I think you need to add a control where you put something else that's not water that is equally cold on your face. Because I know that if external temperature is low, your heart rate goes down to reduce circulation so that less heat is lost. Is it the cold temperature of the water or is it the WATER ITSELF that is causing your heart rate to go down?,(reply>), Shock is the opposite of fight or flight.  Look it up.  Athletic people can have lower heart rate in shock which is probably the explanation here.,(reply>), +Marcus DiMarco vasodilation and heart rate are different things. when your fight or flight response is activated due to shock your heart rate increased and you get vasoCONSTRICTION.,(reply>), +wendy3212 its actually vasodialation from the shock response. lowers heartrate.  Any type of shock initially lowers heart rate.,(reply>), +wendy3212 it's the cold temperature....