While at sea Elephant Seals are solitary and spend 80% to 90% of their time deep under water. They dive routinely to 1000 to 2000 feet (300 to 700 meters) staying down typically for periods of one-half hour before returning to the surface to breathe for 2-3 minutes. Individual seals have been known to dive to over 5000 feet and to stay down as long as 2 hours. This behavior continues, uninterrupted by visits to land or longer periods on the surface, 24 hours a day for periods of several months. Elephant seals do not sleep in any conventional sense while at sea. ( http://www.elephantseal.org )