Water reflections "painted" by Debussy
Claude Monet (1840-1926)
88.9 x 91.4 cm, oil on canvas
Monet Mists North Carolina Museum of Art
The main source for this post is the book Images The Piano Music of Claude Debussy by Paul Roberts

Clair de Lune, 1894
Felix Vallotton (1865-1925)
27.1 x 42.7 cm, oil on canvas
Vallotton Moonlight The Met Museum
While we are in the opera as the Impressionists were often and for long hours, here are some of the masterpieces they painted inspired by it:
The Opera Orchestra, circa 1870
Edgar Degas (1834-1917)
56.6 x 46 cm, oil on canvas
Degas Opera Musee d'Orsay
Degas was the Impressionist with the strongest connection to music. Music was important to his whole family. His father hosted the famous Monday musical Salons where amateurs, like his sister (an excellent singer), and members of the Opera orchestra, performed. Scenes from backstage, in front of and on the Opera stage, remain the main focus throughout his career.
In the Loge, 1878
Mary Cassatt (1844-1926)
81.28 x 66.04 cm, oil on canvas
Cassat Loge Museum of Fine Arts Boston
Even just by reading Debussy's music titles (Nocturnes, Images, Préludes, Estampes...), we can notice that something has changed in classical music. Narratives or tales are of no importance to this new generation of composers. Their themes are conceptual, almost abstract, dreamy, and surreal. The keyword for this music at the time would be "unexpected". Today that is how we see Impressionist paintings. Debussy is changing standard meter, chords, triads, tones, harmonies...
Here is a link to The Debussy Movie, which was made about Debussy by Ken Russel in 1965. Debussy estate protested against it, finding it banal and overfocused on his intimate life, so the movie didn't enjoy many public screenings.
Although he always dismissed the connection to the Impressionists, like them Debussy was also attracted to Turner's great seascapes and the Japanese woodblock prints of Hokusai and Hiroshige. In his later years, he owned many of these.
Modern music after this generation of composers was unstoppable. Musicians and composers took their inventions and built upon them new ones. Bill Evans was one of the jazz players who after leaving Miles Davis' band and starting his own, used impressionist harmonies and was said to be the pioneer and one of the best modern jazz pianists (Nardis by Bill Evans).
Sources:
Book: Images The Piano Music of Claude Debussy (1996 by Paul Roberts)
3. Debussy: Reflets dans l’eau (pianistlost.com) - interesting linkMicrosoft Word - (washington.edu) - Debussy education and influences, life-long obsession with water
Bing Videos - Debussy film
Sonate pour violon et violoncelle de Ravel — Wikipédia (wikipedia.org)
Impressionism in music Debussy - Search (bing.com)
Lecture 21. Musical Impressionism and Exoticism: Debussy, Ravel and Monet - YouTube
What Makes Debussy Sound French?
Debussy and Impressionism: The Shaping Of Modern Classical Music - CMUSE
Lifestyle | The Influence of Impressionism on The Evolution of Jazz Music.
Microsoft Word - Mozart Studies - Vol 1_ultima corectura 17 ianuarie.docx
Debussy on JSTOR