Cube watermelon and freeze until completely frozen.
Add all ingredients, adding the watermelon last, to the Deluxe Cooking Blender. Replace and lock the lid. Press the wheel to start blending on the CUSTOM BLEND setting increasing to speed 9 for20 seconds, or until the ice is broken down.
Serve immediately, garnish with lime slices if desired.
Notes
To make a non-alcoholic version, omit the rum and add more orange juice.