The mammalian diving reflex 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, humans included. Every animal's diving reflex is triggered specifically by cold water contacting the face. Also, the reflex is always exhibited more dramatically, and thus can grant longer survival, in young people and animals.
On July 16, 2004, a toddler was successfully revived after five hours following an accident in an Australian pond.