This would be lovely on a summer day, but we enjoyed it inside, on a windy March night. You could also make this refreshing drink with strawberries.
- Start a few hours before you'd like the drinks, by freezing the cubed watermelon.
- When you're ready to mix the drinks, squeeze the lime juice into a blender.
- Add the frozen watermelon cubes, icing sugar and rum.
- Blend until smooth and frothy.
- Pour into two glasses and serve.