Finely dice the zucchini, cucumber and tomato. Crush the garlic, and finely chop the onion. Add all to a large bowl along with the fresh basil, 1 tablespoon of the olive oil, lemon juice, salt and pepper. Mix well to combine and refrigerate for 20 minutes.
Step 2
Transfer to a blender along with the water and process until smooth and velvety. Alternatively, add the water to the bowl and use a hand held stick blender to process until smooth. Taste and adjust seasonings if required and add more water for a thinner soup. Cover and refrigerate for a further 15 minutes until chilled. Drizzle with the remaining oil to serve.