The word craft since the 17th century has denoted a vehicle or vessel that is used for transportation on the sea, in the air or in space. But it can be applied to fictional vessels such as time craft, dimensional craft, and probability craft. It is primarily used as the root word to which prefixes are added, as in aircraft, hovercraft, watercraft, sailcraft and spacecraft.
Originally the word craft meant any of a variety of skills or professions. In the nautical tradition, it came to mean any means of catching fish such as nets, fishing rods, etcetera. Fishing boats, as well, were included as a means of catching fish. It is this usage of referring to Fishing boats which has overwhelmed the previous one. And the word "craft" soon became synonymous with any vessel that traveled on water.
Its use as a noun originally was as a group noun, sort of a plural in a singular form, e.g., "There are many craft in the harbor." That way, one needed not distinguish between types of craft. Formerly, large sailing vessels were not all called ships, but were given names according to how many masts they carried and how these were set with sails. Small sailing vessels were not necessarily all called boats either, but had terms of their own.
Eventually it became customary to use the word in the singular, e.g., "What a dilapidated craft!"