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In Greek mythology, two monsters that guarded the narrow passage through which Odysseus had to sail in his wanderings. These waters are now identified with the Strait of Messina. On one shore was Scylla, a monster with six snaky heads, who reached out of her cave to seize and devour six of Odysseus' companions. On the opposite shore was Charybdis, the personification of a whirlpool, who drank down and belched forth the waters three times a day. The shipwrecked Odysseus saved himself by clinging to a tree on the shore until his raft floated to the surface.