A group of emperor penguins swim under the sea ice as viewed from an underwater observation tube. Dr. Paul Ponganis, Scripps Institution of Oceanography, and his team study emperor penguins' diving. Emperors routinely dive to depths of 500 meters. Ponganis examines their pressure tolerance, management of oxygen stores, end-organ tolerance of diving hypoxemia/ischemia, and deep-dive foraging behavior. This information provides insight into human diving physiology and has medical applications for patients whose organs or tissues have been deprived of oxygen due to heart attack, stroke, transplant, among other problems.