diving reflex

noun Physiology.

1. a reflex of humans, other mammals, reptiles, and birds, triggered by immersion in cold water, that slows the heart rate and diverts blood flow to the brain, heart, and lungs: serves to conserve oxygen until breathing resumes and to delay potential brain damage.

n.

1. A reflexive response to diving in many aquatic mammals and birds, characterized by physiological changes that decrease oxygen consumption, such as slowed heart rate and decreased blood flow to the abdominal organs and muscles, until breathing resumes. Though less pronounced, the reflex also occurs in humans, upon submersion in water.