I think much of our inherited stories of sea monsters comes from Norse mythology, but this does not appear to have manifested itself in Scandinavian ballads either as nearly all the ones I have seen cover the same subjects as our ballads and involve nobles, battles and royalty. Whilst they do have a little more magic than ours that magic is pretty much like that in our ballads.

I suppose our seamen suffer enough danger at sea without having to invent even more.