A merchant ship, merchant vessel, trading vessel, or merchantman is a watercraft that transports cargo or carries passengers for hire. This is in contrast to pleasure craft, which are used for personal recreation, and naval ships, which are used for military purposes. They come in myriad sizes and shapes, from inflatable dive boats in Hawaii, to 5,000-passenger casino vessels on the Mississippi River, to tugboats plying New York Harbor, to oil tankers and container ships at major ports, to passenger-carrying submarines in the Caribbean. Many merchant ships operate under a "flag of convenience" from a country other than the home of the vessel's owners, such as Liberia and Panama, which have more favorable maritime laws than other countries. The Greek merchant marine is the largest in the world. Today, the Greek fleet accounts for some 16 per cent of the world's tonnage; this makes it currently the largest single international merchant fleet in the world, albeit not the largest in history. During wars, merchant ships may be used as auxiliaries to the navies of their respective countries, and are called upon to deliver military personnel and materiel. History Definitions The term "commercial vessel" is defined by the United States Coast Guard as any vessel (i.e. boat or ship) engaged in commercial trade or that carries passengers for hire. In English, the term "Merchant Navy" without further clarification is used to refer to the British Merchant Navy; the United States merchant fleet is known as the United States Merchant Marine. Name prefixes Merchant ships' names have a prefix to indicate which kind of vessel they are: CS = Cable Ship/Cable layer LNG = Gas carrier transporting liquefied natural gas LPG = Gas carrier transporting liquefied petroleum gas MFV = Motor Fishing Vessel MS = Motorship MSV = Motor Stand-by Vessel MT = Motor Tanker or Motor Tug Boat MV = Motor/Merchant Vessel MY = Motor Yacht NS = Nuclear Ship RMS = Royal Mail Ship RRS = Royal Research Ship RV = Research Vessel SS = Steam Ship SV = Sailing vessel/Sailing Vessel (although these can be sub coded as type of sailing vessel) Merchant ship categories The UNCTAD review of maritime transport categorizes ships as: oil tankers, bulk (and combination) carriers, general cargo ships, container ships, and "other ships", which includes "liquefied petroleum gas carriers, liquefied natural gas carriers, parcel (chemical) tankers, specialized tankers, reefers, offshore supply, tugs, dredgers, cruise,