Chop the cucumber, shallot, and cilantro leaves into large chunks.
Add to blender, along with the avocado flesh and lightly crushed garlic clove.
Add olive oil, lemon juice, cold water, salt, and pepper.
Blend until smooth. Add more lemon juice and water as needed to achieve the consistency you prefer.
Once desired consistency is reached, cover and place in the fridge for 1 hour before serving to allow the flavors to develop.
Serve the soup cold with a drizzle of olive oil, chopped cilantro, and fresh ground black pepper.