The Viking ship, The Grey Eagle, sank off the coast of central Norway in 1696.  It was not seen again until 1982 when a sand dredging operation accidentally destroyed parts of the ship.  Now archaeologists are working hard to “see” it and document where it lies beneath the water.   http://archaeologynewsnetwork.blogspot.com/2015/05/the-vikings-grave-and-sunken-ship.html#.VWXbQ2AbCt-

Viking ship archaeology