Rim a cocktail glass by using a piece of fresh lime and rub it on the rim. Dip the moistened edge into a small pile of salt on a plate.
In a personal blender, like a Magic Bullet, add watermlon chunks, tequila, Triple Sec, lime juice and agave nectar.
Blend until smooth.
Pour over rimmed cocktail glass with fresh ice.
Notes
It's easy to turn this into a Spicy Watermelon Margarita! Just muddle sliced jalapeno or serrano in the bottom of the glass before adding the rest of the ingredients.
You can make this into a Frozen Margarita by adding the ice to the blender and blending it all up together!
Salting the rim really enhances the flavor experience!
Because the flavor of fresh watermelon will change by the melon, you'll need to taste and adjust the flavors for each drink.
Want to make this a little bit skinnier? You can leave out the agave nectar and it will still taste amazing.
You can save any leftover watermelon juice (not including the tequila and lime, etc.) in an air-tight container for up to 3 days in the refrigerator.