Possible Clues:

• The myth of the freshwater mermaid might get to lie like this
• Temptress along the Rhine
• A Rhine maiden learning to put on a garland
• The myth is she'll have you on the rocks and lie there at last
• Rhine Rock where siren lived
• Rhine rock famed for siren
• Famous Rhine rock
• Rhine rock of siren legend
• Preferred blonde
• This siren meant danger to Rhine boatmen