Diving reflex

Apnea and bradycardia caused by stimulation of nasal or facial receptors with cold water. Optimizes respiration which allows mammals to stay underwater for a long time. It is exhibited strongly in aquatic mammals (seals, otters, dolphins, etc.), but exists in a weaker version in other mammals, including humans. Slowing the heart rate and diverts blood flow to the brain, heart, and lungs; serving to conserve oxygen until breathing resumes and to delay potential brain damage.