Start by removing the rinds off the watermelon and as much seeds as possible and adding it to a blender or food processor

Blend until you have a juice, this will be really fast

Strain trough a fine strainer

Make the herb salt by chopping your herb of choice and mixing in the salt using your fingers

Rim the glass with the herb salt and add ice

Build your cocktail by adding the tequila, fresh lime juice, watermelon juice and topping with sparkling water