Scylla and Charybdis were mythical sea monsters that lived on opposite sides of the Strait of Messina. Scylla was originally a nymph that was transformed into a six-headed monster by the sorceress Circe. Charybdis was a greedy girl transformed by Zeus into a monster that three times a day absorbed and regurgitated the sea waves, endangering passing ships. In Homer's Odyssey, Odysseus and his men had to navigate between the two monsters and lost six men to Scylla while passing through the strait.