Prep the rim: Run a lime wedge around the rim of your glass.
Dip in kosher salt or a 50/50 mix of salt and Tajín. Set aside.
Blend the watermelon: Add watermelon cubes to a blender. Blend until smooth and juicy.
Strain (optional but recommended): Pour the puree through a fine-mesh strainer into a pitcher to remove pulp and any seeds.
This keeps the drink silky.
Add citrus and sweetness: Stir in lime juice and orange juice. Start with 2 tablespoons of agave or simple syrup, then taste. Add more sweetener if your watermelon isn’t very sweet.
Chill briefly: Pop the pitcher in the fridge for 10–15 minutes, or proceed right away if your ingredients are cold.
Serve over ice: Fill salt-rimmed glasses with ice. Pour the mocktail over the ice.
Garnish and enjoy: Add a lime wheel or wedge and a small watermelon triangle.
Sip immediately.