Prior to the development of gunpowder, ship-to-ship combat was conducted by missile fire (archery or heavier throwing weapons), ramming, or boarding. For protection against missile fire, ancient shipwrights improved their vessels with cladding, which was a wood or metal bulwark that protected sailors or rowers. We believe that the Vikings did something similar in their long boats by mounting their shields along the side for protection while at sea.
deichman5