In the bowl of a food processor, purée half of the watermelon until liquified, about 10 seconds.

Add remaining melon, granulated sugar, and lime juice and blitz until smooth, about 5 seconds more.

Pour purée into a flat, shallow plastic container or baking dish. Freeze 1 1/2 to 2 hours, or until edges begin to freeze.

With a rubber spatula, scrape outer edges of container, stirring the partially frozen pieces back into the liquid.

Freeze 1 hour more. Stir again.

Continue stirring every hour, breaking pieces apart with a spatula or dinner fork, until the mixture resembles finely crushed ice. (The entire process will take anywhere from 6-10 stirs, depending on your chosen container, freezer temperature, and whether you prefer a “slushie” or “snowball” consistency.)

Scoop into glasses. Garnish with lime zest, watermelon wedges, or slices of lime. Serve immediately.