News Animals Northern elephant seals sleep just two hours a day at sea The mammals snooze less than 20 minutes at a time during dives Northern elephant seals are deep sleepers. Literally. They dive hundreds of meters below the ocean surface to take naps unbothered by sharks or killer whales. Mark Newman/Getty Images Share this:EmailFacebookTwitterPinterestPocketRedditPrint By Maria Temming April 20, 2023 at 2:00 pm Northern elephant seals are the true masters of the power nap. On long trips out to sea, the seals snooze less than 20 minutes at a time, researchers report in the April 21 Science.