1. In a blender or food processor, blend the watermelon, yogurt or coconut milk, rose water, and salt until quite smooth. If your watermelon isn’t very sweet, add a few tablespoons of honey.
2. Refrigerate the soup until very cold (30 minutes to three hours depending on how cold your ingredients were at the beginning of preparation).
3. Serve in small dessert bowls or cups with a few pistachios on top.