1. Put 4 cups cubed watermelon in a blender.
2. Add 4 cups coconut water to watermelon in the blender.
3. Add the juice of 1 lime to blender. Whiz until smooth.
4. Add 10 ice cubes to blender and blend until frosty.
5. Divide cooler among 4 tall glasses and garnish with mint sprigs.