Longships were sea vessels made and used by the Vikings from the Nordic countries for trade, commerce, exploration, and warfare during the Viking Age. The longship’s design evolved over many years, beginning in the Stone Age with the invention of the umiak and continuing up to the 9th century with the Nydam and Kvalsund ships. The longship appeared in its complete form between the 9th and 13th centuries. The character and appearance of these ships have been reflected in Scandinavian boat-building traditions until today.
The longship is characterized as a graceful, long, narrow, light, wooden boat with a shallow-draft hull designed for speed. The ship's shallow draft allowed navigation in waters only one metre deep and permitted beach landings, while its light weight enabled it to be carried over portages. Longships were also double-ended, the symmetrical bow and stern allowing the ship to reverse direction quickly without having to turn around; this trait proved particularly useful in northern latitudes where icebergs and sea ice posed hazards to navigation. Longships were fitted with oars along almost the entire length of the boat itself. Later versions sported a rectangular sail on a single mast which was used to replace or augment the effort of the rowers, particularly during long journeys.[citation needed] The average speed of Viking ships varied from ship to ship but lay in the range of 5–10 knots and the maximum speed of a longship under favorable conditions was around 15 knots.