UDT were an elite special-purpose force established by the US Navy during Word War II. Their primary function was to destroy enemy defensive obstacles on beaches where U.S. and allied forces were going to make amphibious landings.
U.S Navy SEALs are a special breed of warrior who conduct special operations in any environment but who are uniquely trained and equipped to operate from, around and in maritime areas. SEALs take their name from the environments in which they are trained to operate: Sea – Air & Land.
The United States Naval Special Warfare Development Group (NSWDG), commonly known as DEVGRU and informally by its former name SEAL Team Six (ST6), is one of the United States' four secretive counter-terrorism and Special Mission Units (SMUs).