Cut the avocado flesh into cubes and set one aside for garnish. In a blender, puree the remaining 3 avocados together with the sparkling water, olive oil, ice, salt and pepper. Blend until smooth. Zest the limes and set aside. Stir in the fresh lime juice. Serve the soup in bowls and garnish with the lime zest, red pepper flakes, reserved avocado cubes, fresh herbs, a drizzle of olive oil and a pinch of sea salt.