| Service ships - vessels which serve the merchant fleets and operate in harbors, inland waters and water areas; Depending on the function they perform, service ship can be grouped in four categories:
Ships providing navigation through different waters
Hydrographic ships - Their purpose is to explore seas and oceans, gather data and report to hydrographic bureaus which on their part, compose maps and charts. Hydrographic ships inform seamen on possible weather changes as well. Besides which, they are in charge of all signaling devices and lightships at sea.
交通船（launch）
是用于接送船员、工作人员等的小艇。
供应船（supply boat）
是指在港口用于向运输船供应淡水（水船）、燃油（油船）和物料等专用船舶，如图所示。
引航船（pilot boat）
是专门用于接送引航员登船引航的船舶，其船体涂有明显颜色并有引航标志。
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Pilot boat-Public | Pilot boats - small vessels that carry a pilot to a ship and then bring him back to the port. These pilots steer the ship through rivers and canals from one point to another by showing the safest way to go. It is true that ships have their own pilots to navigate them through different waters but peculiarities and changes of a particular water area are not shown on any guide. Therefore local pilots are needed. And pilot boats too.
Lightships - smaller vessels painted red and equipped with light- and radio-signal devices and anchored at places which are dangerous for ships to pass through (e.g. shallows, rocks). Lightships have begun to decrease in number and are being replaced by navigation buoys.
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Lightship -Public | | 