Just adding a few comments...
We had a prior student who was a midshipman at Merchant Marine visit us. He was a free agent with a 34 ACT and he didn't get into Navy which was his top choice. He asked admissions why and they said it was because he had one D from tenth grade.
NWP is a essentially an Air Force school. My class of 77 had over 40 Falcon Scholars and there were less than 10 from the Navy Foundation. If you're only interested in Navy, that's fine. We were visited by several midshipmen and Navy/Marine officers (including an admiral).
IMO if you're a average (or below) student, a semester at NWP will be far more beneficial in the long run than a semester at college. NWP will teach you time management, how to memorize, and attention to detail.
Also, another benefit of doing ROTC instead is that ROTC is another nomination source.