Place water, avocado, vinegar, green and white onions, lemon juice, chives, parsley, basil leaves and garlic in a blender or a wide mouth jar if using an immersion blender.
Blend just until smooth.
Add olive oil and blend again just until incorporated. Salt and pepper to taste.
Refrigerate for 1-2 hours before using.
Keeps in refrigerator for 3 days.