Where is the Third Fleet primarily based?

The Third Fleet is primarily based in San Diego, California. This fleet is responsible for naval operations in the eastern and northern Pacific Ocean, playing a vital role in supporting the United States' maritime strategy in this region. The strategic location of San Diego allows the Third Fleet to effectively manage its duties, which include training, fleet exercises, and maintaining a presence in the Pacific. Additionally, San Diego provides a major naval base with amenities and infrastructure that support the operations and personnel of the fleet.

Other locations mentioned in the choices, such as Mayport, Norfolk, and Manama, serve different fleets or commands. Mayport is home to the Second Fleet, Norfolk is primarily associated with the Atlantic Fleet, and Manama serves as a base for the Fifth Fleet, which operates in the Persian Gulf, Red Sea, and surrounding regions.