Place the watermelon cubes into the blender, ensuring they are evenly spread out for smooth blending.
4 cups fresh watermelon cubes
Blend on high speed until the mixture is completely smooth and no chunks remain, about 30-45 seconds. The liquid should have a vibrant red color and a slightly frothy top.
4 cups fresh watermelon cubes
Set a fine mesh strainer over a large jug or bowl and pour the blended watermelon through it. Use a spatula or spoon to gently press the pulp, extracting as much liquid as possible while leaving behind fibrous solids.
Juice the lime directly into the strained watermelon liquid, then add the salt. Stir well to combine all flavors evenly, ensuring the salt dissolves completely.
1 lime lime, 0.5 teaspoon salt
Pour the finished Agua Fresca into glasses filled with ice cubes, garnished with additional lime slices if desired. Serve immediately for the freshest flavor.