Since the end of the age of sail a ship has been any large buoyant watercraft. Ships are generally distinguished from boats based on size and cargo or passenger capacity. Ships are used on lakes, seas, and rivers for a variety of activities, such as the transport of people or goods, fishing, entertainment, public safety, and warfare.
Ships and boats have developed alongside mankind. Fishing boats are used by millions of fishermen throughout the world. Military forces operate vessels for combat and to transport and support forces ashore.
A boat is a watercraft of any size designed to float or plane, to provide passage across water. Strictly speaking and uniquely a submarine is a boat as defined by the Royal Navy