Cut the watermelon into chunks, removing seeds if needed.
Blend watermelon, sugar, and juice from one orange until smooth.
(Optional) Strain the mixture through a mesh strainer for a smoother texture.
Pour the liquid into a shallow freezer-safe dish.
Freeze for 1 hour, then scrape with a fork to break up ice crystals.
Repeat scraping every 30–45 minutes for 3 hours until flaky and frozen.
Fluff with a fork before serving.
Scoop into bowls and enjoy immediately or store in freezer for up to a week.