Sources : Sawfish
Isidore of Seville [7th century CE] (Etymologies, Book 12, 6:16): The sawfish (serra) has its name from the saw-toothed crest on its back, with which it cuts a ship when swimming under it.
Vincent de Beauvais (Speculum Natural, bk. xvii, ch. 127): The saw fish swimming hidden beneath the ship cuts through its bottom, so that as the water rushes in, it drowns the crew by its crafty device and gorges itself on their flesh. (Druce translation)
Philippe de Thaon [12th century CE] (Bestiaire): "Quaut veit nes en mer halt . si se leve en halt. | A la nef fait grant laid . ke devant le nef vait | E si retent le vent . que ele, nen ad nent. | Ne la nef entant deure de nent ne pot cure." (When it sees a ship on the high sea it rises up. | To the ship it does great harm, for it goes before the ship I And holds off the wind so that it gets none of it. | Nor can the ship all that time sail on at all. - Druce translation)
Guillaume le Clerc [13th century CE] (Bestiaire): "Les mariners qui par mer vount. | Ne la querent ja encontrer. | Quer cest un grant peril de mer. | Si fait sovent la nef perir. | A qy ele put avenir." - British Library, Cotton Vespasian A. vii. (The mariners who cross the sea | Are not wishful to meet it: | For it is a great peril of the sea. | It often makes the ship to founder | To which it is able to get near." - Druce translation)