Prep the Glass: Rub a lime wedge along the rim of your serving glass, then dip the moistened rim into a small plate of coarse salt.
Fill the Shaker: Fill a cocktail shaker with fresh ice cubes.
Combine Ingredients: Pour the fresh watermelon juice, blanco tequila, fresh lime juice, and agave nectar into the shaker.
Shake Vigorously: Shake well for about 15 seconds until the outside of the cocktail shaker feels completely frosted.
Strain and Serve: Fill your prepared salt-rimmed glass with fresh, dense ice cubes and strain the cocktail beautifully over the top. Garnish with a lime wheel and serve immediately.