Possible Clues:

• Submarine vacated in East River
• River wave, sort of catching tide finally
• French setting for Puccini's 'Il Tabarro'
• Locale of the Île de la Cité
• It can be seen in “A Sunday Afternoon on the Island of La Grande Jatte”
• River beneath 37 Parisian bridges
• River to Le Havre
• It flows to the harbor of Le Havre
• Ile de la Cite's river
• River mentioned in “The Ballad of John and Yoko”