I have it currently. So far it's worked out really well for me
But yeah, it's called the Nexplanon. The Navy can put it in for you at bootcamp if you're willing to wait. A lot of females I know got it at that point.
If you want to get it beforehand, just let your recruiter know because it does take about 2 or 3 weeks to totally heal up. The bruising and all mostly, but your arm is going to be stupid sore for about 2 or 3 days. After that you're free to do whatever. I got mine put in back in February of this year.