MacArthur's authority over naval forces was theater command

Did Douglas MacArthur actually command the Navy in his Pacific theater?

He commanded the joint theater and set objectives, while naval commanders retained responsibility for planning and executing maritime and amphibious operations.

Command of a joint theater includes setting objectives and coordinating the services assigned to it. MacArthur could decide where effort should go and require naval support for an operation. Naval commanders remained responsible for the detailed planning and employment of maritime forces. The distinction explains how authority over a theater relates to the specialist work performed by subordinate commanders.