Chop 4 cups of ripe watermelon into small cubes and place them into the blender.
Add 1/2 cup of plain yogurt, 1 tablespoon of lime juice, and 1 teaspoon of honey or agave syrup to the blender. Secure the lid tightly.
Blend on high until the mixture is smooth, slightly thickened, and uniform in color, about 30 seconds. You should see a vibrant, semi-opaque liquid with no large chunks remaining.
Fill serving glasses with ice cubes, then pour the blended mixture over the ice, allowing it to chill immediately. Observe the mixture’s texture for a slush-like appearance with a smooth surface.
Garnish each glass with fresh mint leaves and thin slices of cucumber on top. The mint should be visibly bright green, and the cucumber slices should be thin and translucent.
Serve immediately with a straw or spoon, enjoying the crisp, herbal aroma and the bright, juicy flavor of the watermelon mixture.