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.