Place the chopped watermelon, garlic cloves, chopped tomatoes, vinegar, salt, and pepper into the large blender or food processor.
Blend on high speed until the mixture is completely smooth and slightly frothy, about 30-40 seconds. Check for a vibrant pink color and smooth texture with no visible chunks.
Slowly pour in the olive oil while the blender runs on low, allowing the oil to emulsify into the mixture for about 10 seconds. The soup should thicken slightly and develop a glossy appearance.
Taste and adjust seasoning if necessary, adding more salt or vinegar as desired. Then, transfer the mixture to a bowl and refrigerate for at least 2 hours to chill thoroughly.
Serve the chilled gazpacho in bowls, garnished with fresh herbs or crumbled cheese if desired. The finished soup should be translucent, vibrant pink, and refreshing in texture.