Scoop out the watermelon with a spoon or melon baller.
Place the watermelon in a single layer on a baking tray.
Freeze overnight or until completely frozen.
Place frozen watermelon in a blender.
Add a few drops of liquid if needed. Be careful not to add too much liquid during blending. Let the watermelon thaw out a little if won't blend.
Blend until smooth.
Serve immediately.
Add a splash of juice or alcohol to the top is desired.
Notes
Be careful not to add to much liquid or you'll be drinking watermelon juice! You can certainly add sugar if you like, but if you use ripe fruit you really don't need it at all. This recipe makes a lot of slushies so I store the frozen watermelon in individual ziplock bags. Mix it up!! I love making tropical real fruit slushies with pineapples, watermelon and cantaloupe!