Because you were commissioned a month earlier. Makes you senior officer.
6 seconds sound clip from the G.I. Jane movie soundboard.
You can hear this line at 01:02:30 in the Blu-ray version of the movie.
Quote context
[...]
- You couldn't even haul your own body weight out of the water today.
- Permission to get dressed, Master Chief.
- Mr. England went out with a stress fracture.
- I'm moving Mr. Wickwire to boat five. That puts you in charge of six.
- Why not McCool? He's the same rank?
- Because you were commissioned a month earlier. Makes you senior officer.
- Remember, there are no bad crews... only bad leaders.
- Actually, no, sir. She's been going head-to-head with the men for some time now.
- So she's lasted eight weeks. That's wonderful. Joan of Arc meets Supergirl.
[...]