A tugboat (tug) is a boat that maneuvers vessels by pushing or towing them.
Tugs move vessels that should not move themselves alone,
such as ships in a crowded harbor a narrow canal, or those that cannot move
themselves, such as barges, disabled ships, or oil platforms.

Tugboats are powerful for their size and strongly built, some are ocean-going.
Some tugboats serve as icebreakers or salvage boats. Early tugboats had
steam engines; today diesel engines are used.