That’s a push boat or tow boat, it has what are called two push knees on a squared off bow for pushing barges. A tugboat has a conventionally shaped bow and doesn’t ordinarily push barges, but it can, it tows them using what’s called a hawser. Tugs are also what assist ships in and out of berths. Ordinarily once the ship is away from the dock and underway the tugs are no longer needed, even in crowded ship channels. I worked in the Houston Ship Channel, inbound and outbound ships even in the crowded inner ship channel (Green’s Bayou, Deer Park) area are on their own, but have a pilot onboard. On outbound ships the pilot stays on board until the ship reaches the sea buoy. The ships owners btw., pay for the tugs and the pilots, it has nothing to do with the DOT, the Fed, or in this case the City of Baltimore. The pilot is the boss however and the tugs don’t depart until he releases them. It would have been highly unusual to see tugs hanging on to an outbound or inbound ship which was not in the inner harbor. Both the harbor tugs and the harbor pilots are independentely owned separate operations, but they operate under the Port Authority. “ Moran” is the big boy in harbor tug operations, especially on the East Coast.