Most prey of penguins inhabit the upper water layers, so penguins generally do not dive to great depths or for long periods.
Most species stay submerged less than a minute.
Macaroni penguin dive depths typically range between 20 to 80 m (66–262 ft.) during the day and are usually less than 20 m (66 ft.) at night.
Gentoo penguins can reach a maximum dive depth of 200 m (656 ft.) although dives are usually from 20 to 100 m (66–328 ft.)
Adélie penguins have been recorded staying under water for nearly six minutes, although most dives are much shorter. They have been recorded diving to as deep as 170 m (558 ft.), although most dives are to less than 50 m (164 ft.)
Chinstraps can reach depths of 121 m (397 ft.), but most dives are less than 50 m (164 ft.) Dives last from 30 seconds to 3 minutes.
Most dives of king penguins last less than four to six minutes, although dives of up to eight minutes have been documented. The maximum recorded depth for a king penguin dive was 343 m (1,125 ft.)
Emperors hunt fast midwater squids and fishes and therefore tend to dive more deeply and remain submerged longer than other penguins. The deepest dive recorded for an emperor penguin was 565 m (1,854 ft.) The longest recorded dive for an emperor penguin was 27.6 minutes. Both of these measurements are considered extremes; most dives are between 21 to 40 m (70-131 ft.) of the surface and last two to eight minutes.
Penguins mainly hunt prey in pelagic (open ocean) waters, however sparse evidence (such as stomach content analysis) suggests that gentoo, yellow-eyed and emperor penguins dive and feed at the benthic (ocean floor) level as well. However, a detailed dive study of southern rockhoppers nesting/feeding off the coastal waters of the Kerguelen Archipelago suggest that benthic feeding is an important part of their diets.
Synchronized diving has been seen for northern rockhopper and Adélie penguins. The behavior is poorly understood and observed only at the surface of the water, although individuals were fitted with time/depth recorders so additional underwater data was recorded and analyzed as part of these studies.
A penguin typically sleeps with its bill tucked behind a flipper, which some scientists believe serves no known purpose in penguins, but is a remnant of ancestral relations to flighted birds. Other researchers believe the behavior may reduce the amount of heat lost through the face, particularly the nostrils.
During the Antarctic winter, when the period of darkness may last more than 20 hours, huddling emperor penguins that are incubating eggs may sleep for most of a 24-hour period.