Dice one cup of watermelon into small cubes.

Puree remaining 2 cups of watermelon in a blender and add vodka, liqueur, lime juice and ice and blend well.

Pour 6 oz martini into each glass, add 1/4 cup remaining watermelon into each, and garnish with watermelon and lime slices.

For non-alcoholic version, add ice cubes and replace with a splash of orange juice.