The U.S. Coast Guard is at the moment a branch of the U.S. Department of Transportation (I thought they were part of the US Armed Services but was eddy-kated by VT_hawkeye, thx). They are sometimes known as the "Coasties".
As a result of the big shake-up currently making its way through Congress, the Coast Guard will probably become a branch of the Office of Homeland Security.
Personally, I'm in favor of it, but only because it means I will be able to call them the "Homeys" or even "Hi C's Homeys". When's the album gonna drop, Yo (Ho Ho)?