Ah cool. The Merchant Marine is basically merchant sailors. Marine as in maritime as in sailing. The reason why they have the academy is to train merchant sailors who can handle the logistical support of the navy in an all hell breaks lose scenario. As a Marine Engineering Systems major I'm being trained to operate and maintain todays supertankers, container ships, ro-ro's (roll on roll off basically a ferry), and so forth. The systems portion of my major focuses more on the design aspect of these ships so I end up with a good hands on experience and the knowledge of the physics behind everything. And basically a Marine is a trained killing machine that lives mostly on land. So I'm mostly a civilian but I end up an officer in the navy reserve or active duty in any branch of the military, an option only this academy has. If you want to look it up go here
http://en.wikipedia.org/wiki/Usmma or here
http://www.usmma.edu/.