While an elephant seal may not stand much of a chance once they are under attack, the shark still has to find them. White sharks apparently feed on seals and sea lions only around rookeries where the chance of finding a sea or sea lion is high. Once the seals migrate out to sea, they are highly dispersed and they spend most of their time searching for food in deep water. Trying to locate a seal in more than 1,800 feet (600 meters) of water depth and over the tremendous expanse of the northeastern Pacific Ocean is just not worth a shark's  effort. So the white sharks seem to only feed on seals where they concentrate, around rookeries.The other thing is that white sharks apparently increase their chances of finding a seal by searching near the water surface. Seals and sea lions must go to the surface to breath. So a shark "knows" that seals and sea lions will always show up on the surface. However, elephant seals only spend 10-15% of their time at the surface. Most of their time at sea is spent underwater.Sea lions spend 40-50% of their time at the surface because they are not as good a diver as elephant seals. However, another difference between seals and sea lions is that seals travel alone and disperse over the great expanses of the open ocean, while sea lions tend to hang out together in rookeries more than seals.At a rookery, there are so many seals coming and going that there is safety in numbers. Only a small number of seals are actually taken out of the number that are coming and going. However, when they're near a rookery, they do make the trip quite fast and spend as little time as possible in the water.