Ok, military people only......um, a little help here?

Ok, so i'm twelve and my parents are going away in four days for about a week in the carribean and they are hiring a marine to take care of me. He is about twenty-one and has many many many marine friends and for one thing, I am totally freaked out. I have never never ever meta marine before. He is a complete stranger in my life, don't laugh at me and call me stupid and all that crap but I am terrified of marines. Oh, and my friends make it worst by telling me all those stories on how marines d this japanese and filipino girl, I mean I know they're cool and all that but i'm still freaked out. Help? Panic or not panic?