Step 1

Add the watermelon to a cocktail shaker, and muddle. Strain this out into another glass to get all the pulp out. You want to get at least 2 ounces of watermelon juice. Add the juice back into the cocktail shaker.

Step 2

Add in the lime juice, vodka, and cointreau. Add a few large cubes of ice, and shake.

Step 3

Strain into a chilled martini glass, and garnish with a wedge of watermelon.