Water surrounds three sides of Logan International Airport, with all departures and arrivals flying over Boston Harbor.
There are a handful of coveted jobs on the Massachusetts Port Authority team that protects the harbor, the Massport Fire Department's Marine Unit.
The $7 million vessel is equipped with water guns that can pump up to 6,000 gallons of water per minute.
"The probability of having a major incident in the ocean is pretty high for us," DeGrace said. "So if we had one of these structures here along the waterfront catch fire, between our boat and (the Boston Fire Department's) boat, we could dump quite a bit of water on it."
Massport's Marine Unit provides a critical piece of mutual aid in fire and rescue operations: not only in the city of Boston, but coastal cities and towns statewide.