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The term watercraft covers a range of different water-borne vehicles including ships, boats, hovercraft and submarines. The term would normally imply some propulsive capability (whether by sail, oar or engine) and hence is distinct from a simple device that merely floats, such as a log raft. ==Terminology== Most watercraft would be described as either a ship or a boat. However, there are numerous craft which many people would consider neither a ship nor a boat, such as: surfboards (when used as a paddle board), underwater robots, seaplanes, jetskis and torpedoes. Although ships are typically larger than boats, the distinction between those two categories is not one of size per se. * Ships typically are large ocean-going vessels. Boats are smaller and travel most often on inland or coastal waters. * A rule of thumb says "a boat can fit on a ship, but a ship can't fit on a boat", and a ship ''usually'' has sufficient size to carry its own boats, such as lifeboats, dinghies, or runabouts. * Local law and regulation may define the exact size (or the number of masts) that distinguishes a ship from a boat. * Traditionally submarines were called "boats", perhaps reflecting their cramped conditions: small size reduces the need for power, and thus the need to surface or snorkel for a supply of the air that running marine diesel engines requires; in contrast, nuclear-powered submarines' reactors supply abundant power without consuming air, and such craft are large, much roomier, and classed as ships in some navies. * A merchant ship is any floating craft that transports cargo for the purpose of earning revenue; in that context, a passenger ship's "cargo" is its passengers. The term "watercraft" (unlike such terms as aircraft or spacecraft) is rarely used to describe any individual object: rather the term serves to unify the category that ranges from jet skis to Aircraft carriers. Such a vessel may be used in saltwater and freshwater; for pleasure, recreation, physical exercise, commerce, transport or military missions. 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「watercraft」の詳細全文を読む スポンサード リンク
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