UAL328 asks, in my opinion, because the Logan4 DP, which 99% of departures at BOS are assigned, calls for an immediate left turn hdg 140 on wheels up (when departing rwy 22R). This takes the flight off to the left and over Boston Harbor, before overflying Castle Island on its way out. Any ships in the harbor when the plane is making this low left turn could present a tall obstacle in the departure path.
2) Could also be company policy. If LNG tankers are passing through the harbor, no flights are allowed to physically overfly the ship. Could just be a pilot trying to see if he has to look out for anything.