If you DOR from Recruit Training or OCS and actually get discharged it is almost certain that your reenlistment code on your DD214 will flag you as not desirable for enlistment. It isn't necessarily a show stopper. It depends on the circumstance of your leaving. The least damaging codes would allow you to come back after a waiver by higher authority. That just means they will take an application. The board may still have a big problem taking you back. Just remember, the Navy isn't having difficulty filling up OCS classes. Keep in mind that most of the references posted above of guys coming back or having the option to come back were DOR from an advanced training program, not an initial program like boot camp or OCS, or had not be discharged before they changed their mind. Check your DD-214 for the RE code at the bottom. Then look up it's meaning on the internet or call a recruiter. If you look it up on the internet make sure you are looking at Navy codes. They vary between the services.