In a large bowl, whisk together the plain yogurt and cold water until you have a smooth, consistent base.
Peel the cucumbers, cut them in half lengthwise, and use a spoon to scrape out the seeds. Finely dice the cucumber and add it to the yogurt mixture.
Stir in the extra virgin olive oil, red wine vinegar, minced garlic, fresh dill, and fresh parsley until well combined.
Season with salt and pepper to taste, then cover and chill in the refrigerator for at least 1 hour to let the flavors meld together.
To serve, ladle the soup into chilled bowls and garnish generously with the finely chopped walnuts.