For the DS9 episode with a similar title, please see "The Ship".
A ship or vessel, in traditional terminology, refers to any seagoing vessel. As mankind took to flight, the term was also applied to airships. As space travel became increasingly popular, the term was later applied to starships.
In the novelization of Star Trek, one of the reasons that Iowa was chosen as the construction site for the USS Enterprise was its proximity to shipping lanes along the Mississippi River – suggesting that, on Earth, maritime activity was still alive and well in the 23rd century.
As described in a stage direction from the final draft script of TOS: "Miri", "pint-sized, one-kid sailboats" were to be visible (among other equipment) in the window of Biggs'toystore.