Chill your watermelon cubes in the fridge before starting.
This makes the drink more refreshing.
Place the watermelon cubes in a blender.
Blend them until smooth and liquid.
Strain the watermelon puree through a fine mesh strainer into a pitcher.
Discard any solids.
Add tequila, Triple Sec, lime juice, and simple syrup to the watermelon juice.
Stir well to combine.
If desired, moisten the rim of your glass with a lime wedge and dip in salt for a salted rim.
Pour the watermelon mixture into the glass and add ice.
Garnish with a lime wedge, serve immediately, and enjoy!