United States Naval Construction Battalions, better known as the Navy Seabees, form the U.S. Naval Construction Force (NCF). The Seabee nickname is a heterograph of the first letters "C B" from the words Construction Battalion. Depending upon context "Seabee" can refer: all enlisted personnel in the USN's occupational field 7 (OF-7), all personnel in the Naval Construction Force (NCF), or Construction Battalion. Seabees serve both in and outside the NCF. During World War II they were plank-holders of both the Naval Combat Demolition Units and the Underwater Demolition Teams (UDTs). The men in the NCF considered these units to be "Seabee". In addition, Seabees served as elements of Cubs, Lions, Acorns and the United States Marine Corps. They also provided the manpower for the top secret CWS Flame Tank Group. Today the Seabees have many special task assignments starting with Camp David and the Naval Support Unit at the Department of State. Seabees serve under both Commanders of the Naval Surface Forces Atlantic/Pacific fleets as well as on many base Public Works and USN diving commands.