The Port of Long Beach requires all deep-draft vessels to be guided from open water to final docking by a port pilot. Nearly all ports in the world do this, and the reason is simple: for someone in a large ship accustomed to navigating the open seas, approaching an unfamiliar port is like driving a bus from an empty stadium parking lot into a narrow, dark alley full of unknown, hidden obstructions. Without a port pilot’s local expertise to direct the ship through the harbor’s unique currents and park it at the correct dock, the world’s fleet would probably be dented and mangled (and the world’s ports in far worse shape).

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– Adapated from "The Docks," by Bill Sharpsteen