A boatswain was an non-commissioned officer who was responsible for mooring, berthing, gangways and decorating them accordingly upon visitation of a high-ranking official or VIP; he/she was also responsible for a formal greeting upon such an arrival by which the crewman will blow a specialized whistle in a stylized manner.
As Tom Paris lead an away mission aboard the Delta Flyer into The Waters in 2375, he prepared his team with a heavy dose of sailor talk. When Seven of Nine arrived aboard, he referred to her as the boatswain, and inquired if she was "ready to shove off?" Unaware of the previous banter about "sailor talk", she asked "What are you talking about, Lieutenant?" (VOY: "Thirty Days")