The long ship was relatively shallow going (allowing for rapid deployment on sandy shores), sporting a rectangular sail and oars along almost its entire length. Oftenmost longships were clinker built, and waterproofed by moss drenched in tar.
Our best evidence for longship construction comes from ship-burials. It was common in Viking society for kings to be buried under a long burial mound in a ship with rich possessions. The Oseberg ship burial in Norway and Sutton Hoo in England are both good examples.