Short answer, yes. I did it. The summer following your freshman year you will go to CORTRAMID (Career Orientation Training for Midshipman). You will spend a week in each Naval community: Surface (on a ship), Sub-Surface (on a ship), Aviation (in a squadron and maybe a fam hop), and Marines (Go play in the dirt and shoot things). The mission is to give you a taste of each community in order to give you a place to start when you think about service selecting. One of which is, DING, you guessed it, Marine Corps.
So if you have a Navy scholarship now don't fret. You can still go Marines. You will be briefed about all of this ad-nausea when you check in so don't worry.
If you got any specific questions, PM me and I'll fill you in.
EDIT: I knew there was a thread about this already -->
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