Southern elephant seals can dive nearly a mile underwater and remain submerged for up to two hours.
Except during breeding season, when they return to their rookeries, elephant seals migrate in search of food. During those long months at sea, they often dive as deep as 4,921 feet below the surface of the ocean—nearly a mile—to catch fish, squid, and other marine life they like to eat.
Elephant seals have a large volume of blood, which means they’re able to hold a large volume of oxygen, allowing them to stay underwater longer than most mammals. Recently, scientists have also learned that the best mammalian divers—whales, otters, beavers, muskrats, and, yes, seals—also have positively charged oxygen-binding proteins, called myoglobins, in their muscles. This allows them to store more oxygen than mammals without these positive charges.
Humans, for comparison, have one-tenth as much myoglobin in their blood. Most untrained humans can hold their breath for about 30 seconds before gasping—something you definitely don’t want to do while deep-diving in the ocean.
Image: Jaap Vink/ Buiten-beeld/Minden Pictures/Corbis