Hallgrímur the Strong lived at Vík in Flateyjardalur in the early 1800s. Grímur was his son. One moonlit winter night, Grímur was lying in wait by the sea, hunting for foxes, when he saw a large and unfamiliar creature come on land. Its body gleamed like the skin of a whale and made a rustling sound like seashells rattling. The creature headed straight towards Grímur. When it had almost reached him, Grímur aimed the gun at its head and fired. Blood poured from the wound and the creature retreated back into the sea, never to be seen again. Gísli Jónasson of Svínarnes recounted this event, as told to him by Grímur himself. Gísli maintained that Grímur was a truthful and honest man.
Þorsteinn M. Jónsson, Gríma hin nýja III, p. 212.
See more monsters here