At some points during the movie, (Master and Commander) you can see some men dressed in uniforms I've never seen before. It's some sort of plain white dress with a beret style blue hat. One of them is seen opening the door for Hollom before Jack gives him the leadership speech, and they're seen while the camera pans back to Jack while the crew is looking at the Galapagos through the spyglasses. Are they Marine sergeants, or some other rank I'm unaware of?