They could cross the open oceans under sail and then switch to oars ... In marked contrast to modern sailboats, the ships' lack of a big, vertical keel meant that they were highly maneuverable ...

Tech tycoon Mike Lynch’s superyacht was found with its keel “partially retracted ... and sunk as a result.” The ship’s mast — one of the tallest in the world at around 240 feet ...

Oar-holes could be closed when under sail, sealing out water in heavy seas. The Vikings built their ships starting with the keel and outer planking, only later adding internal framework and supports.

Regent Seven Seas Cruises has marks the keel laying for Seven Seas Prestige at the Fincantieri shipyard in Marghera, Italy.