Since World War II, the U.S. Navy has trained a variety of sea mammals (dolphins, sea lions and small whales) to perform military tasks. Actually, a lot of this work also involved investigation of how sea mammals are able to find objects underwater much more quickly and accurately than sensors the navy uses. The navy has sought to use the trained sea mammals to find mines, and other underwater objects, as well as enemy frogmen. Currently, several trained sea lions are being used in the Persian Gulf to guard navy ships against underwater terrorists. Sea lions are the preferred sea mammal at the moment, mainly because they can live outside the water, and are this easier to transport and take care of when deployed overseas. Dolphins have been successfully used during the Vietnam and 1991 Gulf wars to detect mines. During the Vietnam war, dolphins were effective in intercepting underwater enemy commandos. The dolphins, however, tend to develop attitude problems and will either refuse to work, or flat out lie, if they feel like it. Sea lions, which have long been trained as entertainers, are easier to handle and nearly as effective underwater. Like military dogs, the sea lions require a human handler who must take the time to develop a bond with the animal.