Prepare the watermelon by removing seedless chunks or cutting away any seeds if present. Measure 4 cups of watermelon chunks and place them into the blender.
Add 1 ounce of tequila and a pinch of salt to the blender with the watermelon. Secure the lid firmly.
Blend on high speed until the mixture is smooth and frothy, about 30-60 seconds. The juice should be uniform in color and texture with no visible chunks.
Pour the blended watermelon mixture through a fine mesh strainer into a pitcher to remove any pulp or fibrous bits, creating a silky liquid.
Serve immediately over ice or chill in the refrigerator. Garnish with a lime wedge or watermelon slice if desired.