OP: Great responses provided. Any NROTC student (but especially Marine Options) should show up in shape and ready to do well on the initial physical fitness test with proper form and high scores. Work out this summer - don't slack off.
Regarding orientation: Every school's different but they will all introduce you to "military discipline, uniform wear, customs and courtesies, drill, physical training, and certain general military training topics" as NavyNOLA notes. They will probably do this in a efficient and expeditious manner that will involve some stress, "encouragement" and individual attention. Often, a senior Marine NCO will lead a lot of this and while you may think it is "boot camp" it most certainly isn't.
Most units post pictures on facebook, websites, etc. Search out your school's site or find others for reference. That can give you an idea of what the experience will be like.