A pilot is a mariner who guides ships through dangerous or congested waters, such as harbors or river mouths. Legally the master remains in command of the ship. The pilot is a senior adviser only. It is one of the oldest, least known professions and yet one of the most important in terms of maritime safety. The economic and environmental risk from today's large cargo ships makes the role of the pilot essential.

By far the most challenging part of any ship's voyage is the passage through the narrow waterways that lead to port and the final docking of the ship. The pilot brings to the ship expertise in handling large vessels in confined waterways and expert local knowledge of the port. In addition to bringing local maritime expertise onboard the pilot also relieves the captain from the economic pressures that can compromise safety. Instead of being part of the ship's crew, pilots are employed locally and therefore act on behalf of the public rather than of the shipowners.

Normally the pilot joins an incoming ship at sea via helicopter or pilot boat and climbs a swaying Jacob's ladder sometimes up 40 feet to the deck of the largest container and tanker ships. With outgoing vessels, a pilot boat returns the pilot to land after the ship has successfully negotiated coastal waters.

Pilots specifically use pilotage techniques relying on nearby visual reference points and local knowledge of tides, swells, currents, depths and shoals that might not be readily identifiable on nautical charts without first hand experience in the waters in question.
Beyond the experience and training of regular ship's captains, pilots also receive special, ongoing training to stay on top of their profession. Pilots are required by law in most major sea ports of the world for large ships.

Harbour pilots may do some or all of the following:

• Board ships by boat or by helicopter

• Advise ship's masters on harbour rules

• Direct the course and speed of ships while they are in the harbour

• Guide ships in and out of the port

• Assist ships to berth (come to a mooring place at a wharf) and unberth with or without the assistance of tugboats

• Perform administrative duties as required

• Assist in maritime rescue operations

• Relieve crew on tugboats and launches

• Consult maps, charts, weather reports, and navigation equipment to determine and direct ship movements.

• Direct courses and speeds of ships, based on specialized knowledge of local winds, weather, water depths, tides, currents, and hazards.

• Give directions to crew members who are steering ships.

• Operate ship-to-shore radios to exchange information needed for ship operations.

• Prevent ships under their navigational control from engaging in unsafe operations.

• Provide assistance to vessels approaching or leaving seacoasts, navigating harbors, and docking and undocking.

• Serve as a vessel's docking master upon arrival at a port and when at a berth.

• Set ships' courses that avoid reefs, outlying shoals, and other hazards, utilizing navigational aids such as lighthouses and buoys.

• Steer ships into and out of berths, or signal tugboat captains to berth and unberth ships.

• Advise ships' masters on harbor rules and customs procedures.

• Learn to operate new technology systems and procedures, through the use of instruction, simulators, and models.

• Maintain and repair boats and equipment.

• Maintain ship logs.

• Oversee cargo storage on or below decks.

• Provide assistance in maritime rescue operations.

• Relieve crew members on tugs and launches.