A sailor, seaman, mariner, or seafarer is a person who works aboard a watercraft as part of its crew, and may work in any one of a number of different fields that are related to the operation and maintenance of a ship. While the term sailor has its etymological roots from sailing, that is a time when sailing ships were the main mode of transport at sea, it now refers to the personnel of all watercraft regardless of the type of vessel, boat or ship. It encompasses people who operate ships professionally, be it for a military (navy) or civilian or for sports or recreation. In a navy, there may be further distinctions: sailor may refer to any member of the navy even if they are based on land, while seaman may refer to a specific enlisted rank. Additionally, fisherman are seen as a distinct type of sailor, that is those engaged in fishing.