I think its possible that the text is simply referring to a whale. Or maybe a big shark. For one thing, the people probably could have been easily
scared just spotting a huge whale surface beside a tiny fishing boat, and I'm sure people could have made up stories about it, extrapolating on what
it actually was and looked like from only small glimpses of the underwater "beast".
Probably didn't take too much to scare people back then.
Or, it could have been some other, now extinct creature. If you believe (as some do) that people did live at the same time as dinosaurs, then it
could have been one of those large, sea-faring lizards.
Or just one of those huge anomalies of legend (like Nessy) that continues to be the only one of its kind, and traveled (or still travels) around the
world's oceans today, undetected by our formidable technology.
That is all.



