A drawing of the gladius fish.
	The Gladius Fish is a medieval fish that was believed to be in the waters in the Middle Ages. The knowledge of this fish comes from a late-medieval manuscript by Lawrens Andrewe.  This fish was called Gladius because the mouth resembled the point of a sword. It often pierced ships and caused them to sink.  Of course in the medieval ages, the fish could be real or imaginary.