Begin by cutting a ripe watermelon into cubes, ensuring you remove any seeds.

In a blender, combine the cubed watermelon, crushed ice, lime or lemon juice, and granulated sugar.

Secure the lid tightly, and blend on high for about 30-45 seconds until smooth and frosty.

Taste the mixture and adjust sweetness by adding more sugar if desired, then blend again for 10-15 seconds.

Pour the slushie into chilled glasses, adding lime wedges or fresh mint leaves for garnish.

Store any leftovers in the freezer in an airtight container and re-blend before serving.