Freeze the watermelon chunks overnight. You can lay them out on a slicone mat in the freezer to make it easier to blend.
Place the frozen watermelon chunks into a food processor or heavy duty blender, along with lime juice, and rice syrup. Allow to sit for 5-10 minutes to slightly thaw.
Blend until smooth. You may need to add some warm water and to help the process along.
You can also add some almond cream and continue to blend to create a more creamy texture and flavor.
Garnish with basil or mint and enjoy immediately.