A fishing boat was sailing north of Iceland when it suddenly heeled, so that it was almost flooded, due to some horrific creature that held on to the gunwale. The part of it that was on board resembled some kind of pincers, but the head and body were outboard. The crew cleft the beast in twain at the gunwale. The part that fell on board was so large that they had to cut it up to get rid of it. They estimated that the whole creature must have been many shiploads.
Source: Sigfús Sigfússon, Íslenzkar þjóðsögur og sagnir V, p. 125.