Maelstroms in the North Atlantic
Tides on the Earth move an immense amount of water on a daily (monthly) basis. As a result, vortices form as all this water has to squeeze through a narrow channel. This makes me wonder whether similar tidal effects influenced the tales of maelstroms at sea. Were they originally as minuscule as those in this video and later became epic tales with each new telling? Nevertheless, they are an awesome example of fluid dynamics.