Whirl′pool′ is a current in a river, which moves in a circle, owing to opposite tides or winds. The two celebrated sea-whirlpools are Charybdis near Sicily and the maelstrom in the North Sea, which are not usually dangerous to ships; but, when the current and the wind are strongly opposed to each other, large ships are driven against the rocks. Whirlpools were dreaded by sailors and many legends arose about them. They were thought to be openings into great caverns, within whose depths lived mermaids and sea-monsters. Norwegian fishermen still believe that, if they can throw a heavy object into the whirlpool, it will close without injuring their ship. See Maelstrom and Scylla.