The United States Navy

In the operational environment, as an expeditionary force specializing in amphibious operations, Marines often embark on Navy ships in order to conduct operations from beyond territorial waters. Marine units deploying as part of a Marine Air-Ground Task Force (MAGTF) operate under the command of the existing Marine chain of command. Although Marine units routinely operate from amphibious assault ships the relationship has evolved over the years much as the "CAG" (Commander of the Carrier Air Group/Wing) does not work for the carrier Commanding Officer (CO), but coordinates with the ship's CO and staff. Some Marine aviation squadrons, usually fixed-wing assigned to Carrier Air Wings (CVW) train and operate alongside Navy squadrons, flying similar missions and often flying sorties together under the cognizance of the "CAG". Aviation is where the Navy and Marine share the most common ground, since aircrews are guided in their use of aircraft by standard procedures outlined in series of publications known as NATOPS manuals.
• United States Coast Guard
Although the Posse Comitatus Act, which prevents federal military personnel from acting in a law enforcement capacity, applies only to the Army and Air Force, Department of Defense rules effectively require the Navy and Marine Corps to act as if Posse Comitatus did apply, preventing them from enforcing Federal law. The United States Coast Guard fulfills this law enforcement role in naval operations. It provides Law Enforcement Detachments (LEDETs) to Navy vessels, where they perform arrests and other law enforcement duties during Navy boarding and interdiction missions. In times of war, or when directed by the President, the Coast Guard operates as a service in the Navy and is subject to the orders of the Secretary of the Navy until it is transferred back to the Department of Homeland Security. At other times, Coast Guard Port Security Units are sent overseas to guard the security of ports and other assets. The Coast Guard also jointly staffs the Navy's Naval Coastal Warfare Groups and Squadrons (the latter of which were known as Harbor Defense Commands until late-2004), which oversee defense efforts in foreign littoral combat and inshore areas. Additionally, Coast Guard and Navy vessels sometimes operate together in search and rescue operations.