Measure out four cups of ripe watermelon chunks and place them into the blender.
Add the fresh mint leaves to the blender, distributing them evenly over the watermelon.
Squeeze the juice of a fresh lime directly into the blender, capturing the bright, citrusy aroma.
Add a cup of ice cubes to the blender to make the drink chilled and icy.
Secure the lid and blend on high for about 30 seconds until the mixture is smooth and frothy, with a vibrant pink color.
Once fully blended, stop the blender and check the texture; it should be thick, cold, and slightly frothy.
Pour the watermelon smoothie into glasses, and garnish with a sprig of mint if desired.
Serve immediately with a straw or a garnish of lime wedge for an extra zesty touch.