Are there Green berets in the Marine Corps?

To my knowledge no. The Green Berets are Army Special forces and without enlisting in the army you wouldn't be able to join. A possible exception to this may be in the Delta Force. But the Marines recently made a special forces unit just as good if not better than the Army Special Forces. Keep in mind though that any special forces training is ridiculously hard, usually requires you to have field experience, and often times people come to you instead of vise versa. So its not really like just signing up for the swim team.