Put the cantaloupe in a blender and finely chop. Add 1⁄2 cup water and continue blending until smooth. Strain the mixture and measure out 6 cups juice (drink or freeze the rest). Pour the juice back into the blender, add another 11⁄2 cups water, the syrup, and the salt, and blend for 30 seconds.
Pour the sorbet base into an ice cream machine and follow the manufacturer’s instructions to freeze until the mixture thickens, 20 to 30 minutes depending on your machine.
Scoop the sorbet into a freezer-proof container. Cover with parchment paper or plastic wrap to prevent ice crystals from developing on the top of the sorbet and close with an airtight lid. Freeze for 4 to 6 hours or overnight before scooping.