Excellent insulation is required if parent and egg are to survive. As well as four layers of scale-like feathers over a thick layer of fat, they have small bills and flippers to conserve heat.
Despite these adaptations, emperor penguins are also designed for life beneath the ice. Once in water, the birds become streamlined, athletic predators, accelerating to speeds of 16 feet per second (five meters per second). Tongues equipped with backward-facing barbs prevent fish, krill, and other prey from escaping.
But what really fascinates, and confounds, scientists is the emperor penguin's abilities as a deep-sea diver.
Recorded dives have lasted 22 minutes, and reached depths of 1,800 feet (550 meters). At 1,200 feet (366 meters) animals are subject to 40 times the barometric pressure they experience at the surface. Oxygen supply to the brain and other organs is severely restricted as air in the lungs is squeezed to a 40th of its usual volume. Huge pressures force nitrogen to dissolve in the blood, a condition which can be deadly.
If not actually crushed to death at such depths, unprotected humans would face other fatal effects, known collectively as barotrauma.
Ponganis said: "Anatomically, penguins have lost air spaces, that is their bones are solid, so they do not suffer from mechanical barotrauma. How they avoid 'the bends,' nitrogen narcosis, or high pressure nervous syndromecommon ailments among humans exposed to pressureis unknown."
Scientists have a better idea why they are able to stay underwater for so long. Research by Ponganis and Kooyman suggests emperor penguins are metabolically adapted to conserve oxygen while swimming. Heart rate and body temperature measurements taken at Penguin Ranch indicate how they do this.
Ponganis said: "It had been hypothesized that hypothermia decreased metabolic rate, and that explained how penguins can dive for such long periods. However, we found that core temperature did not decline during diving, and we think that metabolic demands are lowered due to decreases in heart ratedown to 15 to 20 beats per minute in some dives."
In addition, recent studies suggest that during their descent emperor penguins cut off blood supply to much of the body. In effect, all but the most essential organs are shut down. This helps not only to conserve oxygen but reduces the risk of nitrogen getting in the bloodstream.
As a physician, Ponganis believes a deeper understanding of the emperor penguin's physiology could benefit human patients.
He said: "How their organs can survive such decreased blood flow and low oxygen levels during a dive is potentially relevant to how we might be able to treat human organs to better survive heart attacks and peripheral vascular disease because in both situations the organs experience very low blood flow and oxygen delivery."
Similarly, he says, the study of emperor penguins could enable us to preserve for longer organs intended for transplant.
They may look comical, out there on the ice, but don't be fooled. For us humans, emperor penguins could be a potential lifesaver.