The deepest-diving penguins are emperor penguins, who also dive deeper than any birds. Typically, they plunge 100–200m (330–650ft) into the chilly depths of the Southern Ocean around Antarctica as they hunt for krill and fish.
The deepest penguin dive on record was more than 550m (1,800ft). In 2013, an emperor carrying an electronic tag stayed underwater for more than half an hour, breaking previous records by five minutes.
The penguins keep warm with an outer waterproof layer of contour feathers, paired with an undercoat of fluffy after-feathers and plumules that trap insulating air next to the skin.