Other forms: tugboats
A tugboat is a water craft that's used to move other boats by pushing or pulling them.
In an active harbor, you'll often see tugboats assisting larger vessels as they maneuver in or out of the crowded area. Tugboat engines are typically fairly strong, so they can tow — or tug — boats that are bigger. Some tugboats also help move boats that can't steer or power themselves, like barges or ships that are disabled.