A pilot is person who guides ships through dangerous or congested waters, such as harbors or river mouth. Pilots are expert shiphandlers who possess detailed knowledge of local waterways. Pilots are responsible under the law and maritime custom for conducting the safe navigation of the vessel.
In a seagoing constrained with pilots the most popular applied signal flags:
Signal flag H (hotel)
"Pilot on board"
Signal flag G (Golf)
"I require a pilot"
Normally the pilot joins an incoming ship at sea via helicopter or pilot boat and climbs a pilot ladder sometimes up ~12 metres to the deck of the largest container and tanker ships. Climbing the pilot ladder can be dangerous, even more so in rough seas considering that both the ship to be piloted and the pilot's own vessel are usually both moving.