Fill a glass with ice. layer the watermelon pieces in with the ice. Pour one ounce of tequila over the watermelon.
Cut the lime in half and thinly slice a few lime wheels to be used as garnish. Juice the lime and add to the drink.
If if you like a sweeter drink add one ounce of simple syrup into the drink. If you don't like sweet drink or if you want a lower calorie drink skip this. I enjoy this cocktail both ways it just depends on my mood.
Finish by topping the cocktail with lime flavored sparkling water. Garnish with a lime wheel. If you want to get extra fancy you can also garnish with fresh mint leaves, basil or edible flowers.