Staff members of U.S. Naval Forces Southern Command, U.S. 4th Fleet stand in ranks during the Naval Forces Southern Command, 4th Fleet change of command ceremony at Naval Station Mayport. Rear Adm. Victor G. Guillory relieved Rear Adm. Joseph D. Kernan as Naval Forces Southern Command, 4th Fleet commander. Naval Forces Southern Command, 4th Fleet is responsible for U.S. Navy ships, aircraft and submarines operating in the Caribbean, Central and South America and the surrounding waters.