Cut your watermelon into chunks and add it to the blender.
Cut your lime in half and squeeze the juice with a lime/lemon squeezer or your hands.
Add tequila to your liking & ice cubes. Blend & taste. If you prefer it sweeter, add just one teaspoon of simple syrup.
Notes
A lime squeezer is a great investment love using limes as flavorings for fruits, cocktails, and coolers. If you don't taste enough of the lime by hand squeezing, you can use two.The drink should be sweet enough on its own, but a teaspoon of simple syrup will give it more of a sugary bar cocktail taste.