tugboat
A small, strong boat that pushes or pulls big ships.
A tugboat is a small but remarkably powerful boat designed to push or pull much larger ships. Despite being tiny compared to the vessels they move, tugboats have enormous engines that generate tremendous pushing and pulling force.
Tugboats do their most important work in harbors and narrow waterways where big ships struggle to maneuver on their own. A massive cargo ship or ocean liner might cross an entire ocean under its own power, but when it needs to dock at a port, tugboats come alongside to guide it safely into position. The big ship is like an elephant: powerful in open space but clumsy in tight quarters. The tugboat is like the elephant's handler, small but skilled at guiding something much larger.
These boats typically have thick rubber bumpers on their sides and front to absorb impact when they press against larger vessels. Their crews are highly skilled at knowing exactly where and how hard to push. Watch a tugboat at work and you'll see it seems to dance around a giant ship, pushing here, pulling there, working with other tugs to rotate or slide the ship precisely where it needs to go. Without tugboats, modern shipping ports couldn't function: those giant container ships and tankers simply can't navigate crowded harbors safely on their own.