A submarine is a watercraft capable of independent operation underwater. It differs from a submersible, which has more limited underwater capability. The term is also sometimes used historically or colloquially to refer to remotely operated vehicles and robots, as well as medium-sized or smaller vessels, such as the midget submarine and the wet sub. Submarines are referred to as boats rather than ships irrespective of their size.
US Virginia-class submarine underway in Groton, Connecticut, July 2004
Russian Akula-class submarine of the Northern Fleet, in 2008
An early submersible craft, built by Cornelis Drebbel, propelled by oars
1806 illustration by Robert Fulton showing a "plunging boat"
A watercraft or waterborne vessel is any vehicle designed for travel across or through water bodies, such as a boat, ship, hovercraft, submersible or submarine.
A dinghy
A 17th-century sailing raft in Paita harbour (Peru).
A Severn-class lifeboat in Poole Harbour, Dorset, England.