Cute Young Blonde Girl On The Big Ship

Ships can usually be distinguished from boats based on size and the ship's ability to operate independently for extended periods. A commonly used rule of thumb is that if one vessel can carry another, the larger of the two is a ship. Dinghies are carried on sailing yachts as small as 35 feet (10.67 m), clearly not ships; this rule of thumb is not foolproof.
In the age of sail, a "ship" was a sailing vessel with at least three square-rigged masts and a full bowsprit; other types of vessel were also defined by their sailplan, e.g. barque, brigantine, etc.
A number of large vessels are usually referred to as boats. Submarines are a prime example. Other types of large vessel which are traditionally called boats are the Great Lakes freighter, the riverboat, and the ferryboat. Though large enough to carry their own boats and heavy cargoes, these vessels are designed for operation on inland or protected coastal waters.
In most maritime traditions ships have individual names, and modern ships may belong to a ship class often named after its first ship. In English, a ship is traditionally referred to as "she", even if named after a man, but this is not universal usage; some journalistic style guides advise using "it", others advise "she" and "her".