1. The Marine Corps is an Independent Branch, But Serves Under the Navy
Although both the Navy and the Marine Corps are regarded as separate branches of the military, the Marine Corps is technically a part of the U.S. Navy, ever since Congress placed the Marines under the Navy in 1834. That means that while the commandant of the U.S. Marine Corps reports to the secretary of the Navy, the Navy is its own entity, so the secretary of the Navy reports directly up the chain to the secretary of defense.
https://www.uso.org/stories/3128-what-is-the-difference-between-navy-vs-marines
Okay, Navy Junior.