When assigned to a cutter, the new ensign either becomes a deck officer in training or an engineering officer in training. They do everything from standing watch to serving as morale officer, intelligence officer, etc. depending on the needs of the service.
The Coast Guard, while not part of the DOD, is one of the armed services. All military salute superiors regardless of the service. There is a lot of coordination between the CG and Navy. Check out the
United States Coast Guard - Home Page web site for more on this.