Directions

1. Line a rimmed baking pan with parchment paper. Slice off ends of limes; place cut side down on a cutting board. Slice down sides of limes to remove skin and white pith with a paring knife. Working with 1 lime at a time, hold lime over a small bowl; gently cut along sides of membranes to release each segment. Transfer limes to prepared pan; add watermelon and pineapple and freeze at least 5 hours or up to overnight.

2. Purée agave nectar, mint, frozen fruit and 1 3/4 cups water in a blender on high until smooth, scraping down sides occasionally; freeze, uncovered, 15 minutes. Makes about 5 cups lime mixture.

3. Divide lime mixture into 4 bowls; garnish with mint leaves, if desired.