In a medium saucepan, bring 1½ cups water, sugar, corn syrup, and salt to a boil over medium-high heat, stirring occasionally, until sugar is dissolved. Remove from heat. Add mint, and let cool completely. Discard mint.
In the container of a blender, place watermelon; process until smooth. Strain through a fine-mesh sieve into a bowl, pressing with a spatula (there should be about 2 cups juice). Discard solids. Add sugar mixture, lime zest and juice to watermelon juice; refrigerate until very cold.
Pour mixture into an ice cream freezer, and process according to manufacturer’s instructions. Spoon into a freezer-safe container, and freeze until firm. Let sorbet stand at room temperature a few minutes to soften before serving. Using a spring-loaded ice cream scoop, scoop into serving dishes. Garnish with lime and mint, if desired.
Recipe by Louisiana Cookin' at https://louisianacookin.com/watermelon-lime-sorbet/