Collier is a historical term used to describe a bulk cargo ship designed to carry coal, especially for naval use by coal-fired warships. In the late 18th century a number of wooden-hulled sailing colliers gained fame after being adapted for use in voyages of exploration in the South Pacific, for which their flat-bottomed hulls and sturdy construction made them well suited. The first aircraft carrier in the United States Navy was a converted Collier, fitted with a large elevated flat deck, before the invention of purpose built aircraft carrier hulls.

For many years, the Durham and Northumberland coalfields supplied the rapidly expanding London with vast tonnages of coal, and a large fleet of coastal colliers travelled up and down the east coast of England loaded with "black diamonds". Sir Charles Palmer pioneered the construction iron-hulled steam colliers at his Jarrow shipyard, which began to rapidly replace the earlier wooden ships. This inadvertently led to the eventual decline of the glassmaking industry on Tyneside and Wearside, as prior to this, they had had access to large supplies of sand, used as ballast in the wooden colliers returning from London. The iron colliers had ballast tanks which meant water could simply be pumped in, greatly reducing the turnaround time as the sand no longer needed to be loaded and unloaded. Coal was also exported to Europe, and wooden colliers returned with goods such as roofing tiles in their holds.

Since the end of the age of sail a ship has been any large buoyant marine vessel. 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. Historically, a "ship" was a vessel with sails rigged in a specific manner.

Ships and boats have developed alongside mankind. In armed conflict and in daily life they have become an integral part of modern commercial and military systems. Fishing boats are used by millions of fishermen throughout the world. Military forces operate vessels for combat and to transport and support forces ashore. Commercial vessels, nearly 35,000 in number, carried 7.4 billion tons of cargo in 2007.

Ships were key in history's great explorations and scientific and technological development. Navigators such as Zheng He spread such inventions as the compass and gunpowder. Ships have been used for such purposes as colonization and the slave trade, and have served scientific, cultural, and humanitarian needs. After the 16th century, new crops that had come from and to the Americas via the European seafarers significantly contributed to the world's population growth. Maritime transport has shaped the world's economy into today's energy-intensive pattern.

Alex Collier is an alias of US citizen Ralph Amigron (who has also used Ralph Amagran). As "Collier," he claimed to be a contactee. He alleged that he has been in contact with inhabitants of the Andromeda constellation and purported to have messages to relay from these supposed visitors. "Collier's" Andromedans are of the Nordic aliens type, leaning toward the New Age "space brothers" subtype. Collier's statements include an elaborate "history" of the earth from his aliens' point of view. This secret history has elements of many other conspiracy theory and UFOlogy traditions, including Nibiru, Reptilians, grey aliens, colonizations of Earth by multiple extraterrestrial species, Lemuria, and Atlantis. Statements were made by "Collier" that he has been forced into obscurity due to threats made by "three well dressed men" who were allegedly part of a "Program". No corroboration has been made of any of these claims, either of being a "contactee" or of having been threatened into silence by any government organization. He has been openly accused by members of the UFOlogy community of having merely perpetrated a hoax.