noun
diving reflex
Physiological term for the mammalian diving reflex: a set of automatic responses (bradycardia, peripheral vasoconstriction, etc.) triggered by breath-holding and cold water on the face.
潜水反射は、顔が冷たい水に触れると心拍数が下がる反応です。
The diving reflex is a response where the heart rate drops when the face touches cold water.
Compound of 潜水 (sensui, 'diving') and 反射 (hansha, 'reflex'). The term is a direct calque of the English 'diving reflex'.