Add all of the ingredients to a high powered blender and blend on high for about 30 seconds, until smooth.
Save the limes after you have used the lime juice, and cut them into wedges. Pour the watermelon juice into a pitcher, add a few lime wedges to the pitcher, and let it sit overnight (or at least for a few hours in the fridge).
When you are ready to serve, pour the limeade over ice and garnish with a lime wedge.