Scylla sea-monster

Scylla was a sea-monster who haunted the rocks of a narrow strait opposite the whirlpool of Kharybdis (Charybdis). Ships who sailed too close to her rocks would lose six men to her ravenous, darting heads.
Homer describes Scylla as a creature with twelve dangling feet, six long necks and grisly heads lined with a triple row of sharp teeth.