Go to: SEALs SEALs, which stand for Sea, Air, Land, are the U.S. Navy's primary and most acclaimed special operations forces unit. Operating mainly in tight 16-man teams, SEALs train for missions in maritime environments, the desert, the jungle, in cold weather, and in urban surroundings. SEALs are trained extensively and rigorously in and around San Diego, California, and Norfolk, Virginia, to withstand and thrive in the face of personal, physical, environmental and other challenges. A final phase of their training is known as "Hell Week." SEALs trace their history to the frogmen of World War II, although new threats -- including terrorism -- have forced them to evolve substantially in recent years. Specially trained crewmen drive a variety of water craft to support SEALs and other special operations forces during maritime missions, and conduct unconventional small boat operations such as coastal and river patrols.