A ship's boat is a utility boat carried by a larger vessel. Ship's boats have always provided transport between the shore and other ships. Other work done by such boats has varied over time, as technology has changed. In the age of sail, especially for warships, an important role was the collection of drinking water. The use of radio, followed by telex, e-mail, etc. has reduced and then replaced the need for written communications to be delivered. A large enough boat may be needed to carry an anchor to some distance away from the ship, so as to kedge out of a harbour or away from a hazard – and also to recover such an anchor afterwards. Warships have always used their boats as an extension to their military role. This includes the provision of a means of escape for the crews of fireships, the landing of troops, or the "cutting out" raids that were used by the Royal Navy, especially during the Napoleonic Wars. All these requirements competed with the need to be able to stow the boats on board in a way that did not interfere with the normal operation of the ship.
Historically, ship’s boats had different names depending on their role. During the Age of Sail, this included the longboat, captain's gig, jolly boat, and other forms and designations. The terminology was not totally precise and has some variations with time and place. For example, there is reason to believe that the same actual boat could have been issued to one ship as an admiral's barge and then at a later date be used as a captain's pinnace. Similarly, the steam pinnaces issued to warships in the decades around 1900 were habitually called "steam picket boats", so one type of boat had two names.