The United States Coast Guard is one of the 5 branches of the military of the United States. It is a part of the United States Department of Homeland Security. The Coast Guard's purpose is to protect the people, environment, industry and security of the United States on seas, lakes and rivers. To do this, the Coast Guard uses boats, ships, helicopters and airplanes to stop smuggling and other crime and terrorism, and to rescue ships and boats in danger.